I assume you guys are meaning Jackson and his Vic falling out?
I’ll spoiler that for you to make sense
Vic is evicted from her apartment and has nowhere to go. So she takes all her bags and stashed them in his apartment, figuring she stays there the nights she’s not on shift anyway so why not. So she basically moved in without telling him.
Vics friend at the firehouse, Dean, last series rescued a lady from a fire. He started a relationship with her but they broke up. She appeared back a few episodes ago heavily pregnant with his baby. She had the baby and moved into the boathouse with Dean for a few days, when she then abandons the baby with Dean. Vic offers to move into the boathouse with Dean and help him bring up TBD (what he called the baby when he couldn’t think of a name, think he finally calls her Pearl)
So Jackson is pissed because he thinks dean is in love with Vic, but he isn’t. Not yet anyway!
Honestly though if you like greys you’ll like station 19, they’re pretty much the same. Just the crossover a bitch when you’re trying to binge one. Like Chicago PD, Fire and Med.