I got the marriage ending, She announced to get married then went into a room for s**. After that she never showed up, after some days the next act starts about collecting the artifacts, am I missing some context here or is this a bug..? Wasn't sure where to even put this discussion.

Also, when we had to get the traitor (I think frank) from the bandits If I decide to fight and select combatants no one shows up, when I try to add combatants the list is empty, they have combat unlocked and are in the city. not even the mc shows up. so had to pay them, later i loaded the save to select the greg option to avoid paying, but the fight was impossible...any explanations..?

Are you using any mods? Are there any errors listed in the log files? You convinced the princess to marry correct? Then Amelia (the catgirl guild leader) said to wait 3 days? But three days passed and no princess?  Actually, the fact that the next act started is strong evidence that something when wrong, so check the log files.

I didn't scroll..... so embarrassing...
But the other issue is still a mystery, the combat group issue

There's a bug in that quest, the battle is actually somewhere else, but it shows up in town. Ignore the battle button in town.