Have any of those with this problem enabled the avast! Settings, Basic, Appearance, Use special graphics effects ?
As it says this is 'nicer, but may slow down performance on some systems.'
I don't see any way of disabling the graphs, but surely this wouldn't matter if the avastUI remains minimised or on one of the options that doesn't display a graph, e.g. Summary (not statistics), Scan Computer or Maintenance sections.