Hi Balázs,
When the 1.2030 was released I downloaded and installed it before it been withdrawn. After that installation it seems that the UC300ETH no longer needs a firmware change when I switch between Mach3 and UCCNC, in fact, I don't even have to switch it off and on again, just close one software and start the other. This is an excellent feature, I don't know when it happened and why, or if it is a side effect of something else or a deliberate action from you or perhaps (which I hope is not the case) just temporary. The previous version I used was the 1.2028 and I am pretty sure that with that release I always had the message about firmware change and the firmware updated every time I switched software.
Anyway, it is very nice not to have to change firmware, it improves start up time and I for one, definitely welcome this since I am switching back and forth. Of course, my goal is to abandon Mach3, but for now I feel this is necessary for me. For this reason I kept 1.2030, because I am not sure if the behavior is the same in 1.2029 as well, and right now I don't seem to be bothered about the bug, the reason for the withdrawal of 1.2030.
This is just for information, so don't spend time on investigating this if you don't know why this is.