I ordered a DSL40CR in January and it was amazing but in April it just stopped working. Sent it back to get fixed but it was deemed beyond repair and they sent a brand new one and it arrived in June. After a few weeks the new amps' volume would fluctuate after maybe 3-4 hours of playing. Got in touch with the shop I bought it from and described the problem, they said it was most likely the tubes so they sent two new ones. After replacing both tubes the volume still fluctuates after it's been played for a few hours.
Please contact our returns department on 01908 375411 and we would be more then happy to arrange for your amplfiier to be looked at by our engineers at the Marshall Factory.