Goodman Games Yearbook #8 has rules for Monster Fumbles.

If you have the DCC Core Book installed, it includes these rules and enables them automatically.

You can disable them via the DCC Core Book setting "Register NPC Fumble Tables".

There is not a separate setting for Fumble Table on NPCs, it uses the Crit Table. It translates Crit Tables III-IV-V to Fumble table H.

By default the system rolls a flat 1d10 for monster fumbles when Crit/Fumble automation is enabled.

Rules-as-Written (Yearbook #8), a different fumble die is rolled if the target is a PC and they have a Luck modifier other than zero: the formula moves up or down the dice chain one die for each Luck modifier step (so a PC with +3 Luck would cause the NPC/Monster to roll 1d16 on the fumble table rather than 1d10, and a −3-Luck PC would cause 1d6).

You can have the system do this automatically by enabling the Monster fumbles (Yearbook #8) setting (see System Settings) and targeting the PC(s). When several PCs are targeted, the highest Luck applies. Otherwise you can do it by hand after an automatic fumble: click on the fumble table, adjust the formula, and roll manually.

Note: this is separate from, and supersedes, the DCC Quality of Life module's monster-fumble handling — if dcc-qol is active, leave the system setting off and let the module manage it.

You can use the Elemental Crit/Fumble table by setting the Crit Table of your elemental to 'EL'.