Issue
There is a known but unresolved memory leak that occurs with IE as RPA continues to interact with IE over long periods of time.
Until you are able to use Chrome or Edge instead of Internet Explorer, the workaround is below.
Resolution
Set up your botflow to close the IE application and re-open it (using 'Open App' action) after processing a number of records (for example 50). Intermittently closing IE will help resolve the memory issue as you process many records.
To accomplish this, the botflow will need to call another task that closes and re-opens IE every X records that are processed.