TeXmacs 2.5.1 Linux/flatpak directory problem

Hello,

Note: I am a computer scientist.

I am now regretting moving to TeXmacs 2.1.5 because it fails to see 
anything in my home directory excepting the Documents folder and its 
contents.

I installed the flatpak version on my Linux desktop. There's no package 
for my distribution. I had flatpak check the installation. (flatpak 
repair) I've had no other trouble with flatpak which I use extensively 
and have for years.

When I try to open a TeXmacs document that is not in the tree rooted at 
~/Documents by double clicking it fails. For example a file in my home 
directory itself. (If I try to use the open file dialog such a document 
in my home directory is not even visible, nor any other directories 
there excepting ~/Documents.)

I get an "Error messages" titled new window with an error line in it 
that I cannot copy. Here it is, typed in.

Warning: Load error for /run/user/1000/doc/7f6c91bf/blah.tm, Success

When I go to the extended message in this window it says an exception 
was thrown followed by a segmentation fault. The exception message says 
it cannot concretize a tuple, and the description of the tuple is too 
long for the line in the window even maximized, so the end of the 
message is lost.

How should I proceed?

Carl.