For some reason only happens in sculpt mode. Subdividing in object mode seems to work fine.

Hey, it happened to me also, when I investigate it further, I think it triggers when you try to subdivide a model that has vertices which connected with more than 4 edges.

Similar problems here.
Here is a terrain model.

If you do multires subdivision, spikes occour. Seems to be independent from Object mode / Sculpt mode. After subdivision step, poles turn to something like this.

Spikes only occour on vertex poles.

After subdivision step, some loops on poles show artifacts, too.

There is something curious.
Try erase all multires subdiv stages. Now, you can do fresh multires/subdivisions without any artifact.

Do Artifacts on landscape mesh occour, if subdivide is applied to an edited multires stage?

The 'knight.blend1' example file seems to change its multires/subdiv behaviour too. If I sculpt on a pole area on the hips, supdivisions turns whole model into a confetti which swallows whole figure.

Workaround seems to do all subdivision steps in Object mode on the beginning of the sculpting session, before doing anything in sculpting mode. Playing with it atm, but I cant say much more this moment.

Happy blending.

Hello, any news on this yet?

Hi AIRedd

Looks like this bug is still there, in Blender 2.80rc1.

I uploaded a more minimal file.

Only some multires subdivision needed to show problem.