R5 Won't Allow Dependable Focus with Older Model 70-200 f2.8

[johndd]

After I purchased the R5, I immediately had focusing problems with my long lens. I have an Canon adapter to use my older lenses. I was told I needed to upgrade my R5 software, and after I managed that, the focusing issue disappeared. After several months of not needing/using the long lens, I now have the same issue with focusing. Any ideas? 

[deebatman316]

Which model EF 70-200mm F/2.8L USM lens do you have. Canon has released 3 IS models and 1 non-IS model. So please provide the full name of the lens you own.