I have this problem as well. I got etap in early 2016 and didn’t have the problem but got a Wifli RD this year and it happens to me now. Using the FD seems to clear it as noted but I think it might clear itself after a while, too. I wonder if it could be a feature to protect the RD from too many shifts in too short a period? I don’t think it’s a specific battery problem as I have few batteries and they all seem to do it.