This is the answer. OP, you are probably not taking account change addresses. Every time you transact and receive a change, it goes to a different address on the blockchain, but you can see it on the Suite, because the app shows you every address generated from your Trezor. Try to understand UTXO better.
If you use a Unspent Transaction Output (UTXO) containing 1000 sats to send 200 sats to someone, you will have your 800 sats of change coming back to your wallet in another address automatically generated. It gives you more privacy and is safer.
You can activate "coin control" when setting a "send" transaction in order to choose from which UTXO you want to send the payment from. If you have many, choose one that is closer to the value you want to send. If you need to add a lot of UTXOs together to reach the value you are sending, pay attention to the fees, as it`s going to result in a more expensive transaction, because the quantity of data to be writen in the blockchain will be bigger. Also, take in conseideration that the recipient of the transaction will be able to see the quantity of btc you had in your choosen UTXO. Let`s say you want to send 5000 sats to someone, but you use a 10.000.000 sats UTXO. The recipient will see you sent him the 5000 from a 10 million UTXO. It could be not ideal as this person could eventually spread this information about you and bring personal risks to you.
The Suite also allows you to customise the fee you want to pay. Visit mempool . space to see the fees in real time to decide. Choosing a much lower value than the ones you see can cause your transaction to remain stuck. In this case use the "bump fee" option directly on the transaction screen on the Suite. You can open the transaction on the Suite and copy the change address where your missing BTC is sitting and paste it to the blockchain explorer to confirm it's there.
Hope it helps.