This seems to be the same bug as #3008; the fix reported there also works for this...
This certainly looks like the correct fix to me. (I also checked that it fixes my...
Eigenvectors are missing
Installing from maxima-5.35.1.tar.gz requires Makeinfo
Limits behave incorrectly when applied to derivatives
Incorrect simplification: trigsimp(integrate(sqrt(4 - cosh(x)^2),x))
The integration bug is indeed fixed as far as I can see, and risplit-signum appears...
Here is a slightly simplified version of the patch. [Edit: simplified once more]