Following an adjustment, Team Approach will recompute and summarize an account's entire transaction history, reapplying the Giving Level logic for each given Activity Type. This may change the Current Activity as well. As a result, you will find that manual changes made to an account's Account Activity record will be overwritten following an adjustment unless the "Lock Activity?" flag was set. This is intended functionality because any significant change to a previous gift, regardless of age, could impact the account's Current Activity and Giving Level. This functionality also applies if you are using a script that includes a recompute of account activities.
When posting other transactions, such as gifts or pledge payments, the account activities are not recomputed from scratch. Instead, the totals from the current batch are simply added to the existing totals in account activities, the assumption being that the data for the related Account Activity record is the same as if a full recompute were executed. Recomputing from scratch would be an unnecessary use of processing power in this case.