Sliding Sunroof not fully closing

Sold my RS4 today and already missing having something fun to drive so need to get my mk1 back on the road. It's an 83 gti and on the long list of problems is the sunroof. Over time it stopped closing fully, and would just sag a bit in the front right corner (other corners all looked like they were sat back in the right spot).

I think water had got in the seals and rusted the mechanism closed which was a fun job to sort out, so I took it all out and replaced some bits that were worn/rusted, regreased it all and put it back in with a new seal. 

Was hoping that would have sorted my issue out but it still sits low in the same corner, tried pushing it up from inside with some of the fittings loosened off and that didn't help at all. 

The shape of the sunroof panel doesn't appear to have warped at all but really struggling to figure out what else might be causing this. 

Hoping someone else has come across this or can offer up some ideas?

Here is a guide to adjusting the sunroof which you may find helpful.

https://www.thesamba.com/vw/archives/manuals/vwsunroof_h2o/SunroofManual_WatercooledVW.pdf