m 14800 (itunes Ver >10), hashcat has a strange behaviour

[GrepItAll]

Have you tried using a larger mask or a wordlist yet? It could be that you're not providing enough work to the GPUs. Although as Philsmd pointed out, 14800 is an obscenely slow algorithm. Also, has Passware ever managed to crack an iOS 10 or higher backup encryption password for you? It could be that it's attempting to process it as an iOS 9 backup password, hence the much higher speeds (10,000 iterations of PBKDF2 instead of 10mil)