Breeding problem with TMs, advice please? - SOLVED I think

[Lythania]

I am moderately familiar with breeding and have bred a small number of different pokemon in the past. I'm trying to become more familiar with breeding, and I've hit a brick wall with my first current-gen project. I know how to pass down TM moves, but for whatever reason, I just can't get this to work.

To explain: I taught 4 TM moves to a female moon ball Gastly, leveled it up until I wouldn't be in danger of the DayCare making it override moves upon leveling up, and then bred it with a Ditto. I heard that females can now pass on TM moves just like the males, so I was confused when my first batch of new baby Gastlys popped out without any of the TM moves.

I tried to breed a male with the Ditto just in case, and had the same result. I tried to breed a male and a female together, and those babies came out with one of the TM moves: Shadow Ball. (I know that the babies had Shadow Ball because it's a move that Gastly learns naturally upon leveling up.)

It's been a while since I've tried to breed TM moves, and I know that I'm likely missing something extremely obvious here about TM move inheritance. Would someone care to enlighten me? I'd appreciate it.

(Sidenote: Is this thread in the right forum section? If not, please let me know where I should post it, then I'll delete this one and repost it in the appropriate section. Thank you!)