From PR:

In Cura version 4.7 a bug regarding slowdowns in circular perimeters was
introduced (or at list gets triggered much more easily than in earlier
versions):
https://github.com/Ultimaker/Cura/issues/8321

This issue makes v4.7.x hardly usable.
Sticking to v4.5 has become quite "tricky" to say the least, due to
the massive python-induced dependency hell and lots of dependencies
being too new and/or incompatible for the 4.5 version.

Version 4.8 has been released on November 10 that fixes this glitch in
the simplification algorithm. The issue is still open, but is considered
to be solved with 4.8 and changed default settings for Maximum resolution
and Maximum Deviation.

From the Changelog of 4.8:
Fixed under-simplification (blobs, zits) on some printer models. An oversight
in 4.6.x resulted in an oversimplification (smoothing) of models.
The attempted fix in 4.7.x overcompensated, which gave difficulty
(zits, blobs) for some printer models when the resulting gcode became
too intricate. This is now fixed, though some profiles might need
to be updated, since they where made against 4.6.x, and therefore may
rely on the over-simplification.

PR: ports/251236
Submitted by: Sebastian <sko@rostwald.de>