> 1) When max-height is provided, the actual frame height is calculated in
 > ll 8736ff of window.el (as of commit
 > 5746202c182a9c69c732beb29b8507a6e6364799), and that just multiplies by
 > the char-height, which excludes the line-spacing.  This is the buggy
 > case.

I attached a fix.  Please try it.

Many thanks for the report, martin