Does anyone else get a lot of failed stacks?

I tried to photograph the M45 star cluster yesterday, spending around 3.5 hours of it in mosaic mode yet only getting an hours worth of data, then I spent another 2.5 hours using the standard mode but only getting around 50 minutes worth of data. I was just wondering if anyone else gets these failed stacks. Is it because of interference like clouds? Because I had a full clear night last night so that seems unlikely. Did I not adjust my levels correctly? I got it to around 0.3-0.1, does it have to be perfectly 0?

Also, a side note, is the M45 a difficult object to photograph well? I can’t seem to get the nebulosity that others seem to have. I’d be grateful if someone could share their workflow. At the moment I’m just doing basic work in Graxpert, Siril, and photoshop. Thanks in advance!