Could be related to a report I did that has been solved : T68826 ?

FWIW (didn't know that abbreviation ;)
If you do the same thing : Open the blend file, select the Area.001 light (in the outliner). Delete it. Select the Plane.001 object in the Outliner = it doesn't disappear !
Perhaps it can help you great and courageous devs.

Open the blend file, select the Area.001 light. Delete it. Select the Plane.001 object (in the viewport, not in the Outliner) = it disappears.

In fact when I go back to cycles, the object is appearing but I can't select it either. However I can select lights etc...

The bug I encounter is the same as in T70106

It works well on windows 10. It is Mac OS related bug

It worked with 2.81 alpha builds 3 or 4 days before.

I confirm the bug is present on all my MacOsx with AMD RX580, Intel graphics or GTX980. Mojave and High Sierra.

Edit THE cube, Duplicate it in edit mode, create new material and assign new material to the new one. The second material won't show up in Eevee

But test on a blank scene with THE cube with multiple materials. It is simpler

The file arrived some seconds before you answered I think ;)

Oh ! No need to download the file... In fact you can reproduce this on a blank scene..
Edit THE cube, Duplicate it in edit mode, create new material and assign new material to the new one. Bug in Eevee

@William Reynish (billreynish) : Can you reproduce the performance issue with the files I uploaded ? Have you a file I can test ? I am here if you need.
Having to replace the BSDF shader with standard shaders or having to delete objects to recover from performance issues is a pain (even if I can live with it...) This a lot of trials and errors.
I hope somebody will confirm someday and that a fix will be found...

Found a workaround !!!!
Replace Principled BSDF with a glossy or diffuse shader for the materials that have an impact on the performance. Everything runs smoothly.
I will continue to look for the parameter in the principled BSDF that makes the interface slow. Perhaps I will find something.

Tested with another scene "SimpleBoolersBot" which is extremely laggy too:
2 possibilities to recover from the extremely slow performance

Tested with RC1 and this the same problem. Is my config not capable of handling such a little scene in 2.8 ?
2 x 2,8 GHz 6-Core Intel Xeon
24 Go 1333 MHz DDR3
Radeon RX 580 8 Go

CarGPSimpleBug3.blend :
Unhide object wheel.001 = performance issue

With the scene "CarGPSimpleBug2"
When I use the "Pneu" material or "Material.004" on Plane.014 viewport becomes laggy every time.

Open the blend file I uploaded. Select the object "Wheel". Add a new material = Slow performance.
Put the material named "Carrosseie" for example on it and there is no performance issue.

Thank you for the bug fix too ! As Isaac Freeman said, it seems that the texture projection from an object doesn't refresh in lookdev. I have to go to cycles render to see it. I would like to know if it's an Eevee limitation too.

Same bug here : T63524

It seems to be the same bug in "T63826: Crashing file."

I have the same crash when i switch to shading with the blend file.

The "crash report" file is from osx if it can help

Same crash with today's 2.8 beta build on High Sierra Macpro and macbook pro.
Tell me if I have to report this crash every 2.8 daily build or if I should stay quiet and not bother you with that.

It crashes in lookdev preview mode and Eevee renderer mode. No problem with wireframe, solid or cycles preview modes. So I agree it is eevee related.

Same crash with today's 2.8 beta build.

Yes Ctrl+T is node wrangler. Deactivating it won't solve the problem.
I always download the most recent build. (Every morning ;)
I am reproducing the crash with blender 2.8 beta build of April the 16th.

I updated Cuda from 410.130 to 418.105 and I have the same issue. Could this be Nvidia related ?
I (and many 3d artists) won't update to Mojave because of Nvidia compatibility issues ...?
I hope it can be solved or at least reproduced by someone.
I also unchecked Cuda in Blender preferences but it doesn't change anything

I tested on windows and there is no crash ! I can only reproduce this on OSX High sierra 10.13.6.

I can reproduce this on every Mac OSX High sierra Blender 2.8 (Mac pros and MacBooks) with factory settings. Haven't tried on Linux or Windows.