We've reproduced this with 2019 and 2020 and are opening a bug.

Recovered (aka, auto-save) files are located here:

/Users/YourUserName/Library/Application Support/SketchUp 2020/working/SKETCHUP/RecoveredFiles/

Is the folder where you're saving the original model being backed up by iCloud by any chance?

If you let me know your email I can search for the crash reports.

I tried to reproduce this with SU2018 and SU2019 but wasn't able to recreate the issue.

Could you post a video or gif of what you're seeing? Also, are you submitting the BugSplats and including your name/email?

If you're on macOS Catalina, you should be running SU2019.3

@mike amos said:

As far as I know my version, 17.2.2555 is the last and latest for V17 make. How there can be ANY updates is what makes me suspicious.

I have opened and closed Sketchup numerous times now now and the allow checking for updates box remains unchecked so I have no idea why this would suddenly happen more than two years after installing V17 make.

It's not alerting you to an update for SU 2017, but rather, alerting you that SU2019.2 is available.

The update message you're seeing is legitimate, and clicking Download Now won't disable your current version of SketchUp. Download Now takes you to https://www.sketchup.com/download/all

See: https://forums.sketchup.com/t/something-different-with-backups-in-2019/87892/23

@rv1974 said:

Example.. I forced (via task manager) a file crash. On reopening v2019 asked whether I'd like to open an autosaved version which didpreserved latest changes (similarly to PS). But untill now I haven't seen a single Autosave file in the project folder.
Maybe v19 creates them in Temp?
@Juju: bot options are V-ed

Auto-save (aka, recovered) files are no longer saved in the same folder as the original SketchUp model; in SketchUp 2019 they are stored here:

C:\Users\YourUserName\AppData\Local\Temp\SKETCHUP\RecoveredFiles