update: I never figured out what caused the particles to explode, but I "fixed" it by creating my own pop speed limit in a pop wrangle. Although it didn't solve the underlying issue, it killed the momentum before it became an issue, so the sim is now fine.

Hello.
I have this scene of tentacles waving around in the mud. Trying to figure out how to prevent areas of the sim that suddenly explode with insane velocities. What typically can cause that in mpm? I don't have this issue when doing lower res sims. I get the sim to how I like it with lower resolution. Then when I do a high res sim random parts of the sim start exploding near collisions.

Here are the steps that I have taken so far.

1. check collisions. Made sure the collisions are setup properly and that fractional frames interpolate properly.
2. Made the material less stiff.
3. Tried to limit maximum speed of particles. Pop speed limit didn't work at all. Tried a pop wrangle. Limited success, but doesn't solve underlying issue.
4. Increased substeps. Tried increasing min substeps and tried higher global substeps, tried lowering CFL condition to force higher min substeps.
5. Made sure affine velocity clamping is on

The last idea I have is to try changing my animated (deforming) colliders to animated (rigid) colliders. Break up the tentacles using voronoi fracture into smaller pieces to allow for animated (rigid) to work. the docs mention that animated (rigid) is the more efficient of the two and higher accurate.

Any other ideas?

edit: Maybe the explosiveness comes from the tentacles pushing the particles into the ground collider underneath it?