Cursor Issues with 27" LG Ultrafine 5K for Mac

Try a SafeBoot  https://support.apple.com/en-us/HT201262

Takes noticeable longer to get to the login screen, does a 5-10 minute disk repair before it fully boots up, and certain system caches, dynamic loader cache, etc. get cleared and rebuilt. You can login and test or not.

Reboot as normal and test.

Get help with video issues on external displays connected to your Mac - Apple Support
 https://support.apple.com/en-us/HT201177

nurselindasue wrote:

Just purchased above 27" Monitor & connected to my 2016 13" MacBook Pro on Mojave, immediately started having weird cursor issues (previously, the same MBP was connected to a 22" LG Ultrafine 4K for Mac & had no cursor issues on Mojave). The cursor will disappear on website links, not showing at all. What gives?

Try resetting NVRAM/PRAM http://support.apple.com/kb/ht1379

nurselindasue wrote:

Oh, glad you asked--looks like I failed to specify that I'm using the external Apple Magic Mouse (not the more recent Magic Mouse 2) & Keyboard with my MBP hooked up to the new 27" LG UltraFine Display--so no, it's an Apple mouse..

So wireless in both instances. I would verify the battery level is good.

Hold the shift option key and click open the Blue Tooth icon in the upper right menu bar>Debug

here you have several options, I might suggest Factory reset all connected Apple devices.

Set up your Apple wireless mouse, keyboard, and ... - Apple Support

nurselindasue wrote:

Just tried that; my cursor is still disappearing when trying to click on a link...it occasionally will show a pointer finger after holding the left click for a few seconds, but usually not.

Just to clarify this is the built in track pad?