Canon camera connect focus stacking issues

[MarkP32]

I have a 70d. I've recently got 8nto macro using the old non-IS 100MM 2 8 lens. Today I found out the delights of using the CCC app to step focus for stacking. It's a bit slow but works fine for the most part except for one annoying thing that I can't figure out. When using the MF function to bracket focus for stacking the app will only focus in one direction. There are three pairs of arrows for stepping the focus forward or backward in differently sized increments. The arrows to the right of the shutter button work fine but the arrows to the left don't do anything.
I was running on the original firmware so thought it might need an upgrade but that made no difference - I'm now running 1.1.3
I haven't tried a different lens so might do that tomorrow but was wondering if anyone had any ideas.
Running Android 11. Have reconnected multiple times, turned the camera on and off, removed and reinserted the battery. Rebooted the phone and reinstalled the CCC software.
Can't think of anything else to try....

[jrhoffman75]

Give Canon a call at 1-800-OK-CANON and report a bug.

[kvbarkley]

It might not be a bug, it might be a function of the lens. Have we established it happens on more than one lens?

[MarkP32]

Not sure why the lens would focus in one direction and not the other. I have two bodies - both 70d - and it does the same thing on both. I have logged a ticket with the Canon support desk. The person I spoke to didn't really seem to know what I meant but he said he would get back to me by Monday.
I will try it with a different lens and see what happens.

[kvbarkley]

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@MarkP32 wrote:
Not sure why the lens would focus in one direction and not the other.
I will try it with a different lens and see what happens.

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Control loops are funny things, especially if there is a lot of backlash or a dead zone in the system when you change direction. They might drive it one direction, and if it overshoots, rather than trying to correct in the reverse direction, just give it a big nudge and try again in the first direction.

But, this appears to be moot.

[MarkP32]

OK - so I rang Canon UK support. the person I spoke to took my details and promised an email or call back within 48 hours.

Nothing.

But. Weirdly, the issue resolved itself. 

I took the batteries out of both cameras and recharged them,

When I replaced the batteries I tried the Macro lens again and it still wouldn't work. So I tried my 100-400 - that one worked.

Then my nifty 50 - that one worked. So I went back to the macro, fully expecting it not to work and, for no apparent reason - it now works.

Solved but no idea how...