Did you ever consider the possibility that the 2c-I may have also been degraded or something? I'm sure you still had a cross-tolerance, but degradation could've also been a factor. My first batch of 2c-e, which was 500mg, I stored it improperly after the initial dose and it was almost completely inactive after only one week and I took MASSIVE amounts with zero psychedelia, but I still got some very dysphoric physical effects and I almost had a panic attack because my heart was beating so fast and I was vomitting profusely.
I didn't even really store it. I was stupid enough to leave the bag of 2c-e open, and sitting right next to my computer monitor for a few days, and I think the air-exposure, as well as the heat from the computer monitor, caused it to degrade very rapidly. lol
My batch of 2ce degraded after a few months. I noticed that I was not tripping as hard as I should have been and it just felt different. It was kind of cool because it turned into a whole other drug itself. It had a much stronger body high and the visuals were not as intense but they were different. The best I can explain them is that the patterns were smaller and more closely knit than 2ce and they also were more soft and fluid looking.
What could I do to stop decomposition altogether then? But wow, makes a lot of sense though, because during the last few months of tripping with 2C-E (I had my last batch of 500 mg for a period of about 5 months), and during the end of my batch the trips visualization was never really as detailed and fast-paced as they were originally, I noticed things looked more fish-eyed/warped, and if I wanted it to start moving faster I'd have to focus for a few seconds which was kinda gay but not too bad, I can definitely feel ya when you say it was it's own thing, because that perfectly describes how it was for me when it was at it's most degraded point.