FMC scratch pad stuck with error message, "Unable 5000 at GIRRR"

[toadlife]

After entering in a wrong altitude on a waypoint, an error popped up on the FMC and could not clear the error from the scratch pad no matter what I tried.
747-400-FMC_Stuck_Message.zip

Please provide documentation references:

Place an x to check the boxes:

• Something found during a flight test
• FCOM reference included (issues are likely to be closed without this)
• checked current FMC revision ident
• Video included (where applicable)
• Screenshot included (where applicable)

Bug reports:

Many remaining issues are likely airframe specific, please provide the livery this bug happens with

Airframe: 747-400

Route was KSFO to KSFO
Departing 28R
Arriving 28R < ARCHI
After selecting ARCHI I would clear discontinuity and then edit the archi waypoint to be lower. At some point I accidentally set one of the waypoint altitudes to something stupid, and the error appeared.

[mSparks43]

On ground recreate

with (default FMS data)
LFLLEGLL01.fms.zip
DEP->RW17L->BUSI2S
EXEC
EGLL ARR->ILS09L->ALES1H
EXEC
Fix discon on page 6
Set cruise altitude to FL310

[mSparks43]

XPD-15268

[mSparks43]

Fix Released in 12.1.0-alpha-5