I haven't ordered any test prop recently..
I did notice my recent order of test e was a bit darker than normal (meaning possibly different oil used, similar color as my Deca...) but haven't experienced any inj site pain.
Is the prop cloudy at all? If so could be over concentrated and just burning, but if so I assume you would have noticed.
I wouldn't think it would be contaminated as quality has always been spot on with M.
Depending on the injection site, I have gotten slight red or swollen pain post injection..but only when I pinned quads, i assumed it was just because I didn't use a long enough needle to get deep enough into the muscle tissue.
Anyway these are just my experiences..and a few possibilities..
hmmm, maybe others could chime in.