The reason they said the comment about Cervelo and SRAM is 2 fold - Internal routings on the cervelo can lead to an unduly high amount of cable friction leading to poor shifting performance - remedied by new housings and/or improved internal routing job. The second is because SRAM 1090 cassettes, in the early runs, had some serious issues with consistency on cog line placement. This resulted in inconsistent shifting adjust throughout the whole cassette.
Now all this aside - your replaceable dropout is loose. Take your wheel off, and tighten the drop out. Then check the alignment of the hanger - odds are it's off. Fix the alignment or buy a new hanger, and then adjust the gearing. done.
The reason it was fine in the trainer was the pressure being exerted on it kept it in place. Flexing over the winter use in the trainer can work it loose and that would explain why it was off as soon as you went outside and why it can be fine and then off with just switching skewers - different alignment and different pressure used to clamp it all. The tighter you clamp it the more outward the hanger and derailleur is swinging.