You may want to make sure the battery isn’t failing. Look for swelling / bloating of the battery. This can be subtle, try spinning the battery on a flat surface - if it spins easily, the surface of the battery is no longer flat. If this is the case, see here. More info about battery issues (such as misreporting charge) in general is here.
Other than that, welcome to the forum - you seem to have the full collection of the most-heard-of issues if I’m not mistaken. You’ll may make a good test case for the ruggedness of the FP2 - let us know how you get on!