I've been using the camera for about a year with adapted manual focus vintage lenses and had no issues at all, being able to take 5-7 photos depending on whether im on 'Cont. Shooting' or 'Spd Priority Cont'. I bought myself an sel50f18f 50mm lens as I wanted something with autofocus capabilities on a budget, and since have realised that with the exact same settings, my buffer seems to have lowered down to 3 for both Continuous and Priority Continuous. I've asked around the chats im already in and nobody seems to know what could be causing it. Hopefully someone here has any ideas, I'll drop below the things ive already been asked and the answers to hopefully help pass by those.

image size/quality setting - raw/jpg
focus modes - it happens on all focus modes and types, including manual focus
shutter speed, iso / f-stop settings - happens on all varients of each
shoot modes - happens on all of the available modes that the camera can shoot with this lens
software update - all the software for the body and lens are fully updated

Thanks in advance