Yes, seems to be the same issue. I just tried replicating his trigger and locked up an emacs window.. here's the backtrace after sigusr2:
Debugger entered--entering a function:
* #f(compiled-function () #<bytecode 0xb893e2c8c539dfa>)()
syntax-ppss()
python-nav-end-of-statement()
python-nav-end-of-block()
python-info-statement-ends-block-p()
python-nav--forward-sexp(-1 nil nil)
python-nav-forward-sexp(-1 nil nil)
python-nav-backward-sexp()
python-info-docstring-p((0 nil 390 34 nil nil 0 nil 427 nil nil))
python-font-lock-syntactic-face-function((0 nil 390 34 nil nil 0 nil 427 nil nil))
font-lock-fontify-syntactically-region(180 1700 nil)
font-lock-default-fontify-region(184 1684 nil)
font-lock-fontify-region(184 1684)
#f(compiled-function (fun) #<bytecode 0x19ba0a4f10e54dbd>)(font-lock-fontify-region)
jit-lock--run-functions(184 1684)
jit-lock-fontify-now(184 1684)
jit-lock-function(184)
redisplay_internal\ \(C\ function\)()
I'll see if I can spin up a version of 29. Been a while since I compiled emacs from scratch... I'm actually surprised that there aren't packages for 28 and 29 more readily available for ubuntu. Not sure what's up with that.