A PNG @1500x1500 can have fast 15MB, same Size JPG has 10% of Size, may be that is causing problems. Since you are on windows, I'm using XNview to modify the pictures and optimize the size. I have always 500x500 and they will be 40-60kb in most times .
For MP3 there are different versions for the Tags available where all informations stored. MP3Tag is a free tool for editing the Tags since I know about MP3 (and that is a long time

) it is well maintained, regular updates and bugfixes.
Using old versions of the Tags can cause also problems
Total Commander is also a neat tool. It is using split screen, nice to copy or move files, a lot more and it can also modify the date of files easily. It is not free, but worse the small money and you can use it by pressing a button at a nag screen.
I'm old, coming from DOS and Norton Commander, can't live without it
