Losing mmr even though you are winning

at the moment my win rate is about 65% so I was climbing a lot recently when I checked my MMR it was at plat 4 meanwhile I only was at gold 3. When I checked again today my MMR is gold 1 meanwhile my rank also is at gold 1, and I think that is very strange for being able to climb very fast but my MMR going down by a lot. Do you know why that is or has something like that happened to you too?
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