Visualisation of surface PDE solution

Thanks a lot - I tried to load the stl a colleague sent me (he wants to mesh a hippo). I can load the geo, and it also looks like a hippo in NgSolve but when I load the file I get the following error

ERROR: TRIG 295 has 2 neighbours!!!!
ERROR: TRIG 300 has 2 neighbours!!!!
ERROR: TRIG 301 has 2 neighbours!!!!
ERROR: TRIG 303 has 2 neighbours!!!!
ERROR: TRIG 652 has 2 neighbours!!!!
ERROR: TRIG 655 has 2 neighbours!!!!
ERROR: TRIG 657 has 2 neighbours!!!!
ERROR: TRIG 659 has 2 neighbours!!!!

And a seg fault when I try to mesh it. I assume that something is wrong with the STL file - is there a way to find out what's going on.

Thanks!
Marie-Therese

I just found a free online stl repair website - so I can mesh the hippo now!

Thanks a lot for all your help so far!