Plan IQ - Prophet Algorithm - End of year Dips

Hi

I have been using prophet to do some forecasting and with my item i have a lot of end of year dips around christmas.

I know IQ has holidays functionality which i have been using.

I have also added a holiday boolean as an explanatory variable to help.

But the forecast is still not diminishing enough on these weeks.

My historical data has a lot of dips around this time so it annoying that prophet not fully picking this up.

As i think prophet treats explanatory variables and related regressors i decided to create a another one where i add in a 1 as a continuous variable and 0 or 0.5 for the weeks where i want the data to dip in future hoping IQ reduces it. But it doesn't seem to be working.

Any tips?