I am not an electrician so my experience is limited, grain of salt advised.
The only real issue I've had with aluminum is with terminal screws where the aluminum softens and loosens up over time. Lots of installs are now using aluminum instead of copper for cost savings. Don't assume the flex to be grounded. It should be but I wouldn't trust it.
I would personally replace it but that's because I've gotten super conservative with electrical after digging into the house of horrors that was my home's electrical system.