There are a few issues I can think of that are happening.
Ubastet is killing sometimes 1, yes 1 troop, 2, 3 with a summons and 4 if they are all equal health. Try 4 firebombs that are low enough to kill with first hit. Happened once for me. Today Ubastet twice only killed 1 opponent for me.
The 4 gem not getting an extra turn is not restricted to the first turn, it also occurs if you do a 4 match too fast, usually before effects from opponent haven’t finished. That might be the same reason as the first turn bug. Try it, it’s the only plausible explanation I have other than random bug.
It is possible, you can match 3 skulls and keep the turn on the first go. It happened to me once vs four fire bombs, I was able to move whilst it was buffing and I just want to get them over fast and I kept the turn. Might be the same bug as the first turn bug. I have been unable to replicate it since. Absolutely 100% happened.
On 5 gem matches sometimes they do not grant an extra turn if they are horizontal and vertical gem matches and you swipe to the left. I am not sure if that relates to doing them too fast as per the first bug.
The exploders are giving too much mana, and there are issues with them. I lost a GW battle last week to a TDS team, who I had got down to TDS only. I was at 75% health on all troops and the TDS on the 4th loop filled up without exploding it’s own colours. There were no reds or purples on the board at all bar 1 red gem, yet if refilled and killed my team eventually. I didn’t video it as I knew it couldn’t loop again, but it did! This appears to be in connection with some kind of ‘pity’ issue, the AI does seem to get angry and make impossible wins if you have been on a roll. So it seems at least.
Frozen is not working properly in combo with doomskulls and mix of skull/doomskulls, player is able to take skull matched whilst frozen and retain the turn in certain conditions.
Mana collected is sometimes not being counted correctly, happened to me with Emperor Liang since 3.4 and also seems to happen when playing too fast.
Hopefully it is this too fast issue and a simple fix, but to the Devs it is not restricted to the first turn only…