Pretty sure I sorted out my problems with the Solo, I'm thinking no one is interested but I'm gonna tell you anyway.
The holes at the bottom of the oven were blocked with little hard black pieces just larger than the oven holes. They didn't look blocked. I had to slightly widen the holes then tip it upside down so the little blockage behind each one could fall out.
Perhaps this was some residue from when I cleaned the oven (which was filthy) months ago & it's heated then hardened & blocked the holes.
I took off the cap & used a vacuum to suck out any excess dust & now the Solo works as I remember it
I also widened the cap hole even more but my looser fitting gong still outperforms the tighter one which must just be air flow.
This thing has been performing so poorly for months now that it's like getting a new vaporizer, it's really not a bad little portable.
Anyway that info is probably all here, I couldn't find it but that's me. It is a long thread so maybe this'll help anyone else who is frustrated with poor airflow & vapour from their Solo.