Only for info.
In my tests for MantisBT 0000135 https://www.cinelerra-gg.org/bugtracker/view.php?id=135
your issue not occur to me.

My OS-Linux is UbuntuStudio-16.04 and
"cinelerra-5.1-ub16-x84_64-static built Feb14 2019 21:20:42"

IgorBeg