I have had just terrible trouble with crashes as well on my brand new MacBook Pro this year, but connecting a LG Ultrafine and a Display Port (or HDMI via a DisplayPort → HDMI cable) display results in an unpredictable, crash-prone environment. It helped a bit to stop using the $300 Belkin dock I bought from apple for the Ultrafine, so it is only serving the third display - but issues abound. I close the MacBook lid to save a bit of performance since I only use the two desktop displays, but sometimes that crashes things. Other times, opening the lid crashes things. If the laptop goes to sleep, I cross my fingers that it won't break. When I switch inputs on my DisplayPort / HDMI display to view my PC desktop, it often crashes - Especially with the DP → HDMI setup/monitor, but also with the play DP cable (this is across two different test displays apart from the Ultrafine). I've even had the SMC fail and had to reset it due to this issue, and it affects my work several times a month. It is a really disappointing, frustrating issue. I've filed the issue reports a few times, but it feels a bit hopeless. I really hope we can get a resolution for this issue, it would be an enormous relief!