Whenever I close my inventory, there is a delay in input for walking and it seems that the inventory is also laggy too. The walking is only delayed after closing the inventory however. This has been happening for 2 days straight and it is not an issue with my internet. I also tested it in other worlds and it was doing the same thing.
This issue is being tracked at MCPE-220980. We currently need more information about the issue. Check the comment section of that report to see what information is needed.