Sleep regression ?!

[Moomin2020]

My LO is 17 weeks tomorrow and I think we might be going through the 4 month sleep regression. She's never slept well during the day but was a great nighttime sleeper up until the last week. She just will not sleep in her crib, my partner and I have been taking it in turns to sit up with her because she will sleep on the sofa downstairs (?). Does anyone know why this would be? She's flat on her back in both situations.
A couple of things have happened developmentally this week - she's started to reach for toys and has learnt to roll over, I've heard that practicing these new things could be the culprit for lack of sleep, however she lays still on the sofa and sleeps for hours, it's just the second you transfer her to her cot she wakes up (again transferring from chest to sofa doesn't seem to be an issue).
I've been considering moving her in to her cot so she has a bit more space, has anyone had success this way? Could it just be that she's outgrown her crib?
Or just any tips to get through this? We are zombies!

[Johnson10]

Following ....

[lampshade50]

Maybe she likes that you're there with her ? Can she roll on the sofa and in her cot ? Maybe she can't roll on the sofa so has more rest there ? For my baby girl this age was the worst. She started rolling and getting stuck and I had to keep rolling her back as she hated being on her tummy. I do recall moving her into her big cot at this age too. Have you tried a sleepyhead ? This kind of worked for a while with mine. I hope the situation improves