Don't think the lemur app and daemon is the problem. so u can keep em if u want or reinstall after.
Just sounds to me in general that something is acting up with your OS,, and I have tried your issue before with others apps, and no matter what I did it ended up doing it again.. but when I did reinstall process then it fine after.
but come to think of it u can also just do an install directly on the drive running Mac without wipe, then it will just overwrite the system files only. But that is the light version of the fix because sometimes it didn't do the job.
if it didn't do the job:
1. Backup drive using Mac with time machine because once in restore mode, the first thing u gonna do is load the Disk Utility, then totally wipe the drive running Mac. Because if u just restore Mac OS directly from the time machine like u normal restore backups if fails(it wipes drive and transfer all files again), then u just get a 100% identical OS again with same bugs with lemur and we don't want that. We want a fresh install but with same User and App settings as before.
2. Close the Disk Manager app and u should get the pop up again saying install Mac OS ect.
select Install and pick the wiped drive.
3. Once all the Install process is done, and it boots Mac for the first time, it asks you to create a new user or if you want to transfer settings from a old Time Machine backup and pick that and the current date of lastest backup. wait to its all done and u should now be ready again.
it can happen that cubase/other vsts claims some files are missing after if that's the case just run the cubase installer again and all should be fine.. else if some settings are missing in cubase u can restore the files from time machine.
but using the Cmd + R will boot you into current installer of what os ver u have..
in your case high Sierra. I will take abit time to boot restore mode because your Mac will download the installer from internet directly , so depends your internet speed.
if u wanna try out Mojave u need too download the install from App Store..
it will kinda so the process same way by taking existing settings and install with new.