I have to admit that GNU TeXmacs is buggy.

And I've fixed some of them by myself or with the help of other contributors.

Please report bugs to https://savannah.gnu.org/bugs/?group=texmacs

And we will fix it as soon as possible.

For the next release: TeXmacs 2.1, we mainly focus on bug fixes.

I'm not sure when you tried, but I'm using it since 2006 and although there are bugs we are steadily improving it and personally I (and many others) use it everyday and do not experience any serious issue, especially in the last versions. Please realize that TeXmacs is a complex piece of software (is typesetting engine + macro language + UI interface together) so is more difficult to maintain than each piece separately.