I noticed recently that I cannot open my .tex files with TeXMaker by double-clicking the corresponding file in PCManFM. It simply starts an empty TeXMaker window instead of the document. If I open the .tex document with TeXMaker from terminal, it works fine. Also I tried double-clicking on the .tex document in Thunar, and it worked correctly too. That is why it looks like something is wrong with PCManFM.
Still, I can open other documents from PCManFM correctly, so I'm not sure whether I understand the nature of the problem well.
Anyway, I hope it is possible to fix this issue.