Yup, just did troubleshooting on the same problem, R7 with Euro-2 18D sets.
Digit Grabber on the CO side, dialing on speakerphone.
If you cup your hand just right, the touchtone from the speaker is picked up by the microphone, and two digits are dialed on thr line, one from the Partner's tone senders, one from the echo.
Solution is to dial with the Mic turned OFF.