Error in mphplot

Dear all,

I recently switched to COMSOL 5.1 on our Debian system, but when using it with MATLAB, I get a quite odd error.

Basically everything seems to work well, but when I try to plot some result using mphplot, I get the following error:

----------------------------------------
Error using strcmp
Too many input arguments.

Error in mphplot/l_getPT (line 485)

Error in mphplot/geomedgeplot (line 289)

Error in mphplot (line 223)
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Other functions like mphgeom or mphmesh do not cause a problem. I also tried the same code on two different installations, one Windows and one Ubuntu and in both other cases it works.

So did anybody experience a similar problem and do you have some suggestions that I can try to fix it?

Thanks already in advance.

Best,
Hannes