Installed OpenCore, SSD loads very slow.

Recently installed OpenCore on my iMac (14.2 - 27” Late 2013) to upgrade from Catalina to Monterey at present. Everything works fine, but my SSD is so slow to load up compared to my original installation.

Used to take 30 secs at most, now it’s like 90 secs to 2 mins.

Any suggestions on what to do? Another installation of OpenCore etc?

Help please and thanks in advance!