The problem could be your general repricer settings- which are there to protect you (not only for unstable stock, but also unstable price decreases).  In your general repricer settings, you may have Both Safe Repricing and Super Safe Repricing Turned On.  

Please note: You only need one or the other or none at all.  

With either option, sku grid is waiting until supplier price decreases stable and remain constant over a period of time before it allows your item to be priced down.  Your supplier item changed price between ~Dates of Supplier Change~ and because you have these settings turned on, sku grid was waiting for that change to remain constant before decreasing your item.Note, now that the price decreases have stabilized, your price has been changed and your selling price is correct based on your override formula.  If you do not want to use the General Repricer Settings, please turn them off.  Also, if you choose to keep them on, you should only have 

1. Please see this video to understand more about the general repricer settings - https://www.youtube.com/watch?v=9BwfvMh9PhA  

After you've made your change -- however you want it in your general repricer settings, you should force reprice your items. 

See this video to learn how to force reprice all items - https://www.youtube.com/watch?v=1zK5V3D_XGg