Ash_735: i'll appreciate if you will make sort of proper bug report, refering to just header corruption and mipmap misidentification without examples and technical description is kinda empty rambling.
I haven't gotten any bug report like that properly sent to me, and i'm sure i'd read one if it was messaged to me i'd fix the problem (maybe even a decade ago ) i haven't received a PM on the forum since 2013 and no bug reports for years before that. The txds it generates when testing mipmaps were all verified to have correct header via rw analyse and it showed no problems, i've tried to verify files it generates also with g-txd but getting g-txd to even work is a pain in the ass.
I did not update the thread in a long time, but those who actually looked, there were like a dozen of so updates every few years on gtagarage, some of the bugs you are refering to probably already didn't exist for a while.
I see that windows 10 scaling has a serious problem with the tool, i can't do much as i don't have a windows 10 environment to test it, if microsoft craps on their own APIs every few years, they could have better backwards compatibility.
Damage to modding my ass.. Think whatever you want to.
The Hero: It supports uncompressed 565 and 4444, at least in vice city mode (i'm not sure it will save them as 16 bit in sa version) - no 1555 sadly, i'm not sure why this would be even useful for?