Was it a bug and I didn't receive training for my player or
Nope. DMI takes ST & FT into account, so what happened is that you got normal training, as always, but there was a stamina drop that week. That's why DMI stayed roughly the same and then continued to raise again.
BBB: 2 (S37 S38); Top tier: 7 (S35 S36 S37 S38 S39 S41 S63); Cup: 9 (S25 S35 S36 S37 S38 S39 S40 S41 S61)