I am in doubt about the Qiblah direction of a Musjid.

Answer

It is not permissible to create unnecessary doubts in the Qiblah direction of a Musjid. When you are at a place, simply follow the Qiblah ruling of that place. Don't enter into any unnecessary dispute on this issue thereby creating problems and unnecessary difficulty, and don't resort to instruments to disprove the Musjid's Qiblah. Follow whatever direction the Mihraab indicates.