The instructions to "take it day 15-26" or "day 1-25" is based on the idea that women all have a 28 day menstrual cycle.
That isn't even the majority of premenopausal women, let alone someone in late perimenopause.
The best thing you can do, if you don't want a more potent progestin that can get rid of bleeding altogether, is modify the 25 days regimen to every day apart from when you get a period.
Then have a break whilst you bleed, & restart.
There's really no point counting 25/28 if that's not when you are bleeding.
Or you could just take it continuously.
You might get some irregular bleeding but it sounds like that's the case anyway.