Avidemux crashing when joining x265 videos

[ShadowWizard]

I originally had some videos in x264 format, and I converted them to x265 format using StaxRip, but I forgot to join the files together before I did it. These files are from my action camera, and are basically where the camera saves one file, and continues recording to another. I generally have no problems joining them when where in x264 format using the "copy" function of Avidemux, however Avisemux is crashing when I try and do it with the converted files. I get "Assert Failed: avformat_write_header(oc, &dict) >= 0 at line 121, file /home/fx/hudso.......... The application has encountered a fatal problem" I then click ok, and get a Visual C++ Runtime error. Then I click OK and the program closes.
I am assuming that Avidemux isn't advanced enough to join x265 files without re-encoding? If that is correct, what can I use to join these files?
Either way, how can I resolve this, without re-encoding the files?

[badyu17]

If the x265 settings are the same you should be able to join them in latest mkvtoolnix gui using append file option.

[jagabo]

AviDemux is a poorly written piece of crap. It crashes all the time, period.

[ShadowWizard]

If the x265 settings are the same you should be able to join them in latest mkvtoolnix gui using append file option.

Thanks, worked great.