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600 EX II-RT's dropping signal



We are wedding photographers who have used Canon 600EX II- RT's for years now. We use them for receptions and lighting the dance floor, speeches, and creative shots. We have never had issues with connectivity until around 2019/2020. All the sudden since, it has been getting worse and happening at more and more venues. We have found our flashes will not stay connected via radio transmitters at certain venues. We do channel searches, place our flashes in different areas, etc, same issue. We will connect for 2 min, then it will disconnect out of no where. We use mainly another 600 EX II RT as the trigger (master) and other 600 EX II RT as slaves. We honestly are sick of it and are thinking of ditching Canon. We haven't heard of any other flash brands having any issues. Only hesitancy we have is that we have already 8 of these purchased from years of buying them and don't want to have to replace them all with a different brand. Has Canon came up with a fix for this or bettering their flash products? I see this is a known issue and it seems the only "solution" is use Line of Sight. Which won't work for how we use them most the time. ANY HELP PLEASE?


Product Expert
Product Expert

Greetings jennybug678,

I'm sorry to hear that you're experiencing some frustration when using your Speedlite flashes. You are performing some of the troubleshooting steps that we recommend like doing a channel search and testing the flashes in different areas.

Please check the contacts the hot shoe of the camera as well as the contacts on the flash unit itself that sits on top of the camera. I understand you have multiple Speedlite 600EX II-RT flashes and if possible, please test the flashes on a different camera body to see if the camera itself the root cause of the issue.

If the above does not apply, then we would need to take into consideration of certain interferences in the event you're shooting at. For example, if the event has a local wireless network, then this may cause wireless connection issues. It doesn't have to necessarily be a physical wireless router and mobile phones that use a hotspot function would transmit a wireless signal that could interfere with the connection on the flash unit.

When shooting in an environment where there may be local interference, we would recommend using the infrared optical wireless connection rather than the radio wireless function.

We are experiencing the same issue as Jenny.  We have tried the channel searches to lose connection.  We have moved the flashes to different connections, we tried new batteries, we tried swapping flashes around from slave to master, etc, only to have our flashes actually one show green and the others red, ie the flash randomly connected to a WiFi signal!  We are at our Witt’s end with the canon speedlite problem.  We have contemporaries using Godex that do not have this problem. Unless Canon solves this problem soon, we will be ditching canon after many years of brand loyalty and tons of flashes.  


We are in the same boat. 
I have been using the Canon 600 EX-RT/ ST-E3 RT system since 2012 when first. Accumulating more over the years, I have 5 600’s and 2 RT Transmitters. All have been working great until Early February 2023. 
Everything you described has been happening since. 
No new router at home. Wife and son not in the house as they were traveling for the weekend. 
Trouble shooting as well if not better than people at Canon, numerous discussions with CPS, we decided to send in for “Repair” and firmware update. The Transmitters were updated, but the 600’s were not. “Sender” in the transmitter, Master and Slave, Not Sender and Reciver. There is a documented situation on Canons site, where 7 or more would “Drop Link” updates were performed in both the Transmitters and 600’s. 
When my units were returned I immediately set up all of the Speedlites. and both Transmitters.  set up just fine only to “Drop Link” one by one after 3-5 minutes. 


Hey there - (not a forum expert and I also don't know how to link you over to other forums) - but there are at least two other forums with tons of comments on this same issue.   One is titled:

Radio communication issues.EL-1, 600EXII-RT, 430EXIII-RT, YN686EX-RT, ST-E3-RT Speedlite Transmitter

and the other is titled:

Canon 600EX II-RT drops link- HELP!

Lots of other folks having the same issue. I too had several Canon flashes and transmitter that I've invested in.  The cheapest solution I could come up with is to use one Godox transmitter (attaches to hot shoe of camera) and get one Godox receiver (per 600 EX slave - set up wherever and the 600EX attaches via the receiver's hotshoe).   I purchased the X1R-C Godox trigger and several X1T-C Godox receivers. I've had one shoot with them so far and they worked well (no link drop).  There's also another Godox trigger (X2) if you want to maintain on-camera flash with off-camera flash 

I posted more details with my observed pros/cons and other tidbits about this approach in the second referenced forum above that may be useful. 

I totally agree - such frustrating results on a system that had previously been rock solid!


I gave up and switched to Godox 860 3C. no problems at all.

Ok thanks! I’ll take a look at them. What GHZ do they run on?



Any updates as to why our once reliable System is now “Unreliable”?

Well, this has been a known issue for a couple of years now, so I wouldn't expect an update any time soon.

Earlier in the thread, a Canon Product Expert said:

"When shooting in an environment where there may be local interference, we would recommend using the infrared optical wireless connection rather than the radio wireless function."