Subscription Plans add extra year

Hi, I'm new to this forum and I have already solved some problems using the information in it.
My problem is with subscription plans adding extra years beyond what the parameters say.  We are not using UPGRADE or RECURRING at this point.

Plan 1 - for 1 year, expiry date is 2021-12-31 - this works fine, no matter how many times I renew it
For example, subscribe today and the subscription is for 2021-03-18 to 2021-12-31.
Each renewal adds 1 calendar year, i.e. ends 2022-12-31, then 2023-12-31 and so on
Plan 2 - for 2 years, expiry date is 2022-12-31 - adds an extra year the first time, after that it is correct in renewing for 2 more years
New subscriber for 2 years, date range is 2021-03-18 to 2023-12-31, one too many.  Renewing for 2 more years expires 2025-12-31
Renew once more and expires 2027-12-31.

Attached is a screenshot of the 2 year plan and the subscription history.
I tried eliminating the expiry date, but our membership years end on Dec 31; this method gave me 2 years from the day I subscribed.
I would appreciate any ideas on how to address this.
Thank you,
Darlene