No playback in previous projects

Neither in version 1.1.40 nor in 1.1.41 is there any playback in my previous projects. Midi keyboard is audible though. If I import a new media project, the playback works. What can be the reason?
When the song is played the first time, the tempo is wrong at the beginning of the first bar (2 beats to tempo 120). After stopping and replaying from the beginning, it runs correctly again.

Did you move the project file or its assets (audio/midi files or folders etc)?
What does your project contain, only MIDI or audio too? Do you see waveforms, or midi events in the Tracks view? We just need more details, thanks.

Yes, we are fixing this.

Yes, I moved the folder to another drive due to space issues. The subfolders there are empty except for projects and templates. That could be the cause. However, it is now not necessary to solve the problem further, since a new import can solve the problem more quickly. Thank you for your help.