Fellow Kerbonaut DasSkelett advised that KSP-Recall should be tagged as a requirement for TweakScale on CKAN, but CKAN don't sort KSP versions - so this would make Recall being installed on everything, including where it is not needed.

Update Recall to allow being installed on anything without peskying the user about - I coded a lot of safeties anyway, and they are working. There's no need for this anymore:

This can be a problem if I'm using something specific for KSP >= 1.8 somewhere - is so, throw the pride through the window and use Reflection. It's too soon to allow KSPe's custom DLL loading to be used by the Mainstream at this moment.

Well, it happened that the code was already safe to be run downto KSP 1.4.1 (99.99% about 1.4.0 too, but I rarely test something on this one).

Fixed on commit d594845