v5 Performance Issue with selections/fill handles on bigger sheets

We are just evaluating to switch from v4 to v5 and experience quite some lagging when selecting areas with the mouse / using fillhandles on bigger sheets in v5 that haven't been an issue with v4.

Scrolling the table is fine, about the same performance as with v4. Selecting areas/using fillhandle has been more or less instant in v4 as well, not so with v5.

Sheet size is 15 columns with 1000 rows.