Inexplicable delay in MacOS dialogue boxes

[woolypants]

What do you mean by "download and use Maintenance"? Is that an Apple application I haven't heard of?

Titanium Software | Operating System Utilities for Mac - Maintenance

Maintenance is an operating system maintenance and cleaning utility for macOS that you can use to perform miscellaneous computer maintenance tasks: run periodic scripts; rebuild the databases; delete application, font, and system caches; and more.

www.titanium-software.fr