Changing 'Non-Recurring' to 'Recurring' Ignores Remaining Subscription Time

I’m hoping I’m doing some ‘small-dumb-thing’ but I have not been able to wrestle this into working.
I want non-recurring customers to have the option to renew with a recurring billing.
Unfortunately, when they choose the ProForm-Stripe option with ‘recurring’, their existing, already paid-for membership is disregarded (the renewal isn’t added to the end of their remaining time).

PS: Another weirdness which may provide a clue?: One member signed-up with ‘recurring’, then moments later signed up AGAIN for the same ‘recurring’ membership (don’t ask me why), but instead of doubling the length of the membership, S2Member only honored the second signup, but Stripe collected both payments.

THANKS! ALL HELP APPRECIATED!

Changing ‘Non-Recurring’ to ‘Recurring’ and to keep Remaining Subscription Time needs some custom code. I sent you a PM.