I went through something similar. I powered through all of Bunpro N5 + N4 for the N4 test in December, then gave myself a “small” break, which turned into a ~4 month break. By that time I’d forgotten most of the subtleties of the new grammar points that I hadn’t already learned and drilled sufficiently in real-life class.
I tried jumping back in for a couple days, but it was too discouraging, especially with the ghosts.
I reset completely back to zero, then have been adding new lessons at a more aggressive pace. E.g. I did 2 chapters of N5 a day for a while, then 1 chapter of N4 every couple days, and now I’m doing something like 1/3 of a chapter every couple of days, depending on how bad my ghost count is. Today is my 40th day study streak, and I just added the last items of N4 chapter 8 to my review queue. My total ghost count is under 40; and ~85% of my grammar points are at SRS level 7 or 8. I feel confident and happy in my grasp of the material. So, resetting worked pretty well for me.
I think one difference between Bunpro and WaniKani is that the total number of items in the SRS is just not that high. N5 + N4 together only have ~250 items, which is between 2-3 levels of WaniKani. It’s not a big burden to reset and re-up the SRS level on every grammar point when there’s only ~250 of them.