There is an issue where, after redelegating the entire staked amount (even after the redelegation period has passed), fees are charged to the previous validator when claiming staking rewards.
At the time of redelegation, it shows as being charged to one validator, but after a few hours, it charges both validators again.
This issue particularly appears in Google extension programs and on mobile, while the Keplr dashboard displays it correctly.
Given that the same issue occurs in the Leap Wallet, it is not exclusive to Keplr.
In my opinion, it seems that there is a tiny amount left over after redelegation to the previous validator, which is not visible, and rewards are claimed for that amount.