Question: Slow boot time after update to Mojave - External SSD
I have a iMac 21" 4k 3,1ghz 2015. I installed an external SSD Samsung 860 Evo 512gb to avoid losing the Apple 1yr warranty if I opened my iMac by myself.
So when I was using APFS format and OSX High Sierra, my iMac used to start, then 2 seconds with a completely empty screen(black) looking for the boot SSD, then the Apple logo appear and it would take another 18 seconds for the system to start completely.
Total boot time = ~20secs.
Now I installed the new MacOS Mojave and my current boot time are very very slow; when I turn on the computer the screen stills black for 2 minutes more or less "looking for my external boot SSD" and then the Apple logo appear and +18secs the system starts.
My current boot time = More than 2~3minutes!!!!
I have also a MacBook Pro 2017 TouchBar and TouchID with 512GB integrated SSD also with APFS format, and update this from High Sierra to Mojave at the same day/time to the iMac. Fortunately the MacBook Pro booting done in about 20secs.
So... There is any solution for fixing this "everlasting" blank screen when booting the iMac with MacOS Mojave and external SSD with APFS format?
I've researched about this, but I can't find anything to solve it. So, I hope someone here may help me!
iMac, macOS Mojave (10.14)