InvalidInstruction
SPL Token · Custom(12) · 0xc
custom program error: 0xc
What it means
The token program could not parse this instruction.
What to do
Client/program version drift — rebuild with a current SPL Token client.
Have the transaction that failed with this?
Paste its signature. TxWhy shows the exact instruction and inner call that raised the error, and rebuilds the transaction when the cause is one it can fix (compute limit, expired blockhash, priority fee, stale swap quote).
Code 12 means something else in other programs
Custom codes are private to each program. Check which program actually raised it: it is the innermost failed call, not necessarily the program you called.