What is DME Unlock?

Reading through a NOTAM I found something I don't understand,

A0311/17 NOTAMR A2635/16
Q) VTBB/QIDXX/I/NBO/A/000/999/1342N10046E025
A) VTBS  B) 1702080225 C) 1705081100
E) ILS DME I-SES CH38X RWY 01R UNUSABLE BEYOND 15DEG
LEFT OF LOC COURSE DUE TO DME UNLOCK


What is DME Unlock? How does it affect the flight?

• Could you post the NOTAM in full (or at least provide the location identifier)? – J. Hougaard Mar 22 '17 at 5:32
• @J.Hougaard added. Now it is very long. The part I am interested in is the last line. – vasin1987 Mar 22 '17 at 5:39