What you describe here is "change address", and that would only affect the overall balance that Trezor displays, an example of that would be your Trezor showing balance of 1
BTC, and then when you copy your current address to one of the blockchain explorers it would show 0.6
BTC, that missing 0.4
BTC belongs to a change address that was created when you made a transfer from your wallet at some point in the past.
OP's problem if I understand it correctly isn't related to that, he mentioned a missing output, so this means, the balance on the explorer is larger than what shows on his Trezor.
I think it may be the "change address" you mention. The balance on the explorer is lower than what is shown on my trezor. My description was a little unclear as I was calmly panicking.
This question posted on the Trezor forum is similar to what I am seeing and the response from Trezor leads to a post about Change Addresses.
https://forum.trezor.io/t/bitcoin-change-being-send-to-a-new-address/14262I am 95% sure that is the correct situation, but I have a nagging question about why I can not see that "Change Address" from within the Trezor, even if I do an export to a CSV.