Some problems with change subscription plan

Hi, I have some problems with change subscription. It will show error.

I think may be problem with this code:

class-form-hanlder: line 1817

if( isset( $_POST['current_subscription'] ) ){

                $subscription = pms_get_member_subscription( absint( $_POST['pms_current_subscription'] ) );

            }

should be change to

if( isset( $_POST['pms_current_subscription'] ) ){

                $subscription = pms_get_member_subscription( absint( $_POST['pms_current_subscription'] ) );

            }

and class-payment-getway-manual.php function process_sign_up line: 77
It can’t get subscription because current getway pay for new subscription plan. But it get current subscription.

$subscription = pms_get_current_subscription_from_tier
so $subscription->update will make an error

I dont know so much about logic to change subscription. I hope author’s plugin will cover this issues.

Another question i want to ask, how about amount of time from last subscription. Can that time add with new subscription plan? And price for new plan?

Thank you so much!
Your plugins very useful and flexibility!