You need to take it in to an authorized Line 6 service centre:
An audio dropout problem potentially exists with older X3 Live units - those with serial numbers less than 21X3LxS59xxxxx..
If your unit's serial number is less than that it qualifies for a free hardware fix that resolves the drop out issue. Take your X3L to the nearest service centre for a free repair under lifetime warranty. Tell the service centre to consult Line 6 Technical Bulletin #52 - this will authorize them to perform the reapir under warranty. I suggest you call them first - they may need to order a part.
If your serial number is higher than the one above then the problem is something else. Please let us know.
Usually you cover the postage one way and Line6 the other.
The UK support centre is:
Line 6 - International
4 Sopwith Way
Drayton Fields Industrial Estate
United Kingdom, NN118PB
Telefon: +44 (0) 1327 302 700
Fax: +44 (0) 1327 302 702
They are very helpful (well always have been for me!)
Yes - that serial number qualifies for the free fix, although as johnpicton says you may be repsonsible for shipping costs.
Also, as a security precaution I suggest you edit your earlier post and delete your serial number.