To M8100 groupset users that use M6100 cassettes...

I just recently fitted my bike with the M8100 groupset but I bought the M6100 cassette instead for durability and cost-cutting plus a 38t Deckas chainring since Shimano doesn't have an official 38t chainring. My problem is, after testing the bike, I noticed that the 5th and 6th cog doesn't shift that well like kakabyos muna saglit then okay na siya(saka need mo i-hold yung pindutan ng shifter para mawala kabyos) while the rest of the cogs are smooth when shifting. Is this a compatibility issue or can just be fixed with a quick trip to a bike shop? I can't visit a bike shop until the weekend so I'm asking this subreddit in advance. Thanks!