My Solo 60 also has an annoying loud howling sound shortly after firing, which fades away after about 30 seconds.
It still only fires off part of the time E02 errors. This is worse if its already hot???
My automatic reset modification that I described above works every time.
My last contact with TT Tecc Support was over 3 months ago. He had me make some internal code changes which didn't work at all, boiler wouldn't fire. He said he would get back to me, which he hasn't. They must be swamped or take notes & loose them like I do or just slide by.
In any case would anyone like to buy a lightly used TT Solo 60? This is the last TT boiler that I will ever buy!