Even though your host states no problem. I would be highly suspicious of "Lost connection to MySQL server during query"
But for the rest of it. I noticed when I upgraded to 7.5 I had similar errors other than the connection issue. I recall about 4 entries but I believe a different line.
Call it coincidence but when I enabled the profile comments. The errors did not return.
To your question about slow I did notice at first that viewing profiles seemed to stall a little but not now. But if you are having Mysql connection issues, that would slow down everything.
But in any case I think this should be in the Bug forum.
