"X protocol error: BadLength (poly request too large or internal Xlib length error) on protocol request 139" is https://debbugs.gnu.org/37895 (amongst others)
This is marked as fixed in Emacs 27.1. If the issue still occurs for you with Emacs 27.1, I suggest reporting it using M-x report-emacs-bug. Reporting Emacs bugs that aren't specific to Debian (eg packaging) as Debian bugs tends not to lead anywhere.
