Sense not tracking swimming correctly

[JS740]

I have a Fitbit Sense and I swim in a swim spa, set it up to automatically detect swimming after 10 minutes.  A week ago I swam 3 days in a row, first day it worked as it did the last few months for me, the next 2 it didn't detect a swim, which wouldn't have had any variation from previous detected swims.

Since I started to manually set the swim, which isn't easy to do on a wet Fitbit with wet fingers, but it is only showing a fraction of what I would normally see for results?

Anyone else experience this or know if there was an update which may have changed things for me, as I am swimming stationary against a current.

Moderator edit: updated subject for clarity

[EdsonFitbit]

Welcome to the Fitbit Community, @JS740.

I'm sorry to hear about the difficulties you experienced with your Fitbit Sense. Thank you for the information provided.

Your Watch should continue tracking your swimming activities with the new firmware version as it used to. If you haven't done so, please perform a restart by following these instructions.

In addition, you can set the pool length to a different value and then set the right pool size again. For instructions, please visit this article and open the menu "How do I set the pool length for my Fitbit device?".

Hope this helps.