Downgrading from Big Sur to Catalina

Started 3 months ago | Discussions thread
kierenlon Contributing Member • Posts: 974
Re: Downgrading from Big Sur to Catalina

wklee wrote:

The Mac seems to take a long time to start. There is maybe a 15 to 30 second lag to click on Macintosh HD or the dock. Downloads or Applications folder for example. Beach balls.

I have downloaded EtreCheck Pro. Will have run it to see what the scan reports.

Good posts by the rest of the forum members.   Symptoms definitely don't sound like an OS version problem.    
It's always good to define the problem as clearly as possibly so you can ensure you are solving for the right thing.   In this case, it seems to be hard disk,  so downgrading would have lead to disappointment. 
If you decide to change the internal disk,  ifixit dot com has guides & tool advice.  As noted, you can boot externally in the short term.

Good luck.  Glad you got to the root of it and reported back - it may help someone else with a similar issue.    The worst thing when looking for a solution online is for the OP to raise a problem (that you also have) then post back with "resolved" with no explanation of what they did to resolve it

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