Do you have to stay with your Employeer after GC approval?
Some say 6 mo, some says 3 mo, but I have not seen any thing concrete.

Has anybody faced any kind of problem due to this issue?

Has anybody faced the problem in citizenship application due to this issue?

I hope not.

I quit the company that sponsored my GC about three months after I got the GC. I haven't faced any issues on the new job or traveling abroad. But it would be nice put my mind at ease.

Any Sajha immigration authorities that have the definitive word on this.

xgaffadi ,
You have to stay with your present employer until 6 months of EAD approval. You can switch your employer after that.
You must've got confused EAD with GC because once you have GC, you can do whatever you want.