file be lock and cannot be save

hello,

I meeting an issue that my project cannot be save. The same time I save a project, I'm getting a red error " The project is locked.". but, When I save to other founder succece, while it couldn't open in normal. That's would be open with nothing. When I open an old normal project ,the project can "only read,couse it been locked by another process". All the projects will creat an *.spp.lock file behind these days.

[SP version  8.1.2]

how can i solve those . THX ：）