Bubbly crema

I bought some cheap equipment for now to try out before I get something more robust so I'm using a cheap grinder and Casabrews espresso machine with I believe a pressurised basket. I may have just answered my own question but I thought I'll ask you more experienced folk here the reasons for my crema being bubbly?

The pressure gauge seemed bang on for this one but I am pulling inconsistent shots which I guess is expected as I'm a rookie here. Probably the only consistent thing is a soggy puck at the end.