Mod Pack: Monster v1.0.3
Mod & Version: Chisel v1.5.0-fix
Pastebin link to crash log: N/A
Whats the bug?: Chisel left-click on valid Chisel-able material blocks can make the block vanish entirely to the player chiseling (no ghost bounding box, nothing). The empty space still collides with the player, but as far as the client is concerned the block is air and the player can interact with blocks otherwise obstructed by the "vanished" block. In SSP and SMP this can be amended by going away a distance (beyond render range) and returning, or by restarting (SSP)/relogging (SMP). Interestingly enough, in SMP, only the player using the Chisel has this issue; other players can see and interact with the vanished block appropriately.
Can it be repeated?: Yep. I didn't go through the whole catalog, but it seems to occur with random selections in variations on Dirt and Fantasy Blocks at the very least. Does not happen with every single variant, but as when you left-click Chisel a block it turns into a random variant this isn't something I'm going to spend a lot of time going through.
Known Fix: Don't use the Chisel like that? (I don't actually use it like that, credit for finding this goes to a certain significant other, who may have chanted "see see, look at me, finding bugs, now you have to report it" while running around turning my mining tunnel's walls into random blocks. I take minor solace knowing tomorrow is historically the busiest work day of the year for his section and he's working help desk during it.)
Mod Pack: Monster v1.0.3
Mod & Version: JABBA 1.0.3 & BetterStorage 0.7.3.38
Pastebin link to crash log: N/A
What's the bug?: Using the Dolly on a stacked (two-high) Locker has fun results. If used on the bottom portion, it makes the locker "disappear", but the top locker is still there and has a "ghost" bounding box and its inventory can be interacted with as normal. Placing this bottom portion elsewhere will show the double Locker entity but you will only interact with what was in the bottom inventory when opening it, and you can walk through the top half of the locker. Picking up the top portion likewise will allow you to move around a "ghost" locker nobody can see. If you move the two pieces responsibly, they'll merge back together into a single locker in the end.
Can it be repeated: Yep.
Known Fix: Don't panic, your stuff is all still there, just split between the two pieces like you'd expect. If all else fails, you can break and replace both. As usual, since this belongs in the catalog of "stupid tricks Vauthil does with mod objects that allow you to pick up things with NBT data", I don't know that anybody's rushing to address this one. Very not critical. (Note: if somebody has done this, you may see a lot of "[WARNING] [betterstorage] getConnectedTileEntity() returned null." in the console until it's put back together right.)