Wow, yeah, I can see how that got stretched a little!
My point was the controller is too fast for the device its talking to, not so much itself.
In the 24 (25 years this October) years I have been using Opto 22 gear, I have never heard or seen what you are describing.
As Mary said, every time I see something that smells like that, its turned out to be my code… And a whole book could be written on the bugs that I have caused over the years!
Im currently in Australia consulting on a project that has around 180 serial devices, we have seen some really ‘interesting’ timing issues with them… and that’s not including the topic of working in autostep on, but not when its off!!!
My point is that when talking to external devices, timing can become a grey area and you need to keep your wits about you.