After Startup Scan gmail won't load

This morning I did a Startup Scan, which I interrupted after some time as it was taking too long. It had moved several items to the sandbox.
When I wanted to read my gmail, it would not load (i.e. it took endless time). Only when I chose ‘simple HTML’ it would work.
Als I saw that several Google icons had changed.
How can I repair this damage and how can I remove items from the sandbox?
Kind regards,
Rob.

PS
Running Windows-10.