We had similar problems the year my daughter wore the Medtronic cgm. We'd had a great six weeks, and then six weeks of what you described daily. It was a real hassle to get Medtronic to send a new transmitter (I wasn't taping carefully so the sensor was wicking in and out of the interstatial fluid was their line.) When the new transmitter arrived, the problems ceased immediately.
I so do not miss dealing with Medtronic customer service!
8/2010 - 9/2011 MDI, Lantus & Humalog
9/2011- Medtronic Revel 723 & CGM
11/2012 - Dexcom G4
2013 - Cut-The-Cord for water times after multiple Aquapac failures
10/2015 - T-slim
"Life is not waiting for the storms to pass, but learning to DANCE in the rain."