The investment gains percentage appears to be based on an incorrect total investment amount once a withdrawal is made.
- Invest an amount (say £100)
- Withdraw an amount (say £50)
- Reinvest that amount (so £50)
The total invested would be 100 - 50 + 50 = 100
I would expect that a gain of say £10, would be reported as 10% (a gain on £100) not 6.7% (a gain on £150)
On Android
On Pixel 8 Pro
Version 5.79.0