In that case, it is an issue.

Try powering down your PS4, waiting 30 seconds and turning it on again.

For the Equipment window issue, is this for any character? There is a known issue like this when first asking a companion to re-join the party, which is fixed if you save and reload (or save and reload in the homestead, before asking them to rejoin).
Equipping from the inventory should work, though isn't filtered and doesn't give access to other characters' inventories.

For the grenades, check the containers in the character's inventory (backpacks, etc, and there is a pouch container with the the same icon as a pouch of moondust or bonedust). It is likely the missing items added to their inventory are being stacked in a container (possibly a crate picked up without looting first, etc).