This is a biggest danger.
I once had a portable DVD player but to be honest I came to the conclusion they were a waste of money when a small laptop does not cost much more and is far more reliable and useful.
The PC usually plays everything, while the desktop or portable players play more or less only the standard DVDs!!!!
Once happened to me on DVD Lab, that the DVD was burned well, everything was correct but the DVD could not be played on any desktop player (no problem on PCs or MACs). After several month experimenting (and discussion also here) I found out that the DVD was not burned to ISO standard, so I had to convert the professional RAW DVD (4 language) into ISO and solved all problems......