Could not save as "xxx.psd" bc of a program error

Hello everyone,

I hope my English is good enough to understand.

So I have a problem and that started with the last two updates. I made a document with the format a2 and 300dpi. I drew in the evening (it was just some strokes for some sketches) and have around 6 layers. I saved it and worked on it the next day I wanted to save it as a new file ( i always save different versions) but suddenly I got a message that it wasn't possible to save bc of a program error. I wondered and changed the amount of ram for photoshop. But I still couldn't save. So I tried to save the file without change and even this wasn't possible. I never got this problem and it comes only sometimes. In some situations, I can reduce the size but this is not always the solution.

Graphic card:  NVIDIA GeForce GT 630

System: Win 10 Pro 64-Bit (10.0)

Prozessor: AMD FX(tm) - 4350 Quad-Core Processor (4CPUs)

Adobe Photoshop Version: 22.1.0 20201125.r.94 2020/11/25: 4b16c876033 x64

I saved photoshop on an external hard disk with USB 3.0

I hope that someone can help me.

Thanks ahead!