This can be a problem with using the reorder script instead of the filter script. (Unfortunately, people on the forums seem to talk about lesson filter, lesson reorder… and even review reorder interchangeably at times. I think the latter two are accomplished with the same script, but I’d argue that each of the three performs a different function with different results that work well for different people - though of course they can be used in combination. I think @Pep95 was actually referring to the last in their recommendations - prioritizing radical/kanji reviews, generally when time for reviewing is limited.)
Unfortunately, I think that Flaming Durtles (which I’ve tried out on your suggestion - thanks! ) has reorder (of both lessons AND reviews) BUT NOT filter. This last allows you to create a mixed/hybrid order that I’ve found helps avoid the problem you’re describing above. I break up the level’s kanji (and vocab) over multiple days (so some kanji and some vocab each day, generally), which means that I guru them in a staggered way. This then staggers the rest of the vocab lessons across the second half of the level.
It seems like this is also the approach that @MissDagger takes, and of course there are variations based on time and ability. But I’m sure either of us would be happy to elaborate on the above if it sounds at all useful And perhaps I can suggest the lesson filter to the Flaming Durtles creator if it seems useful!