Belkin wemo switch offline in Smartthing

Hello all.
Haven’t posted for a while. Glad to be back.
I have 6 of these oldish Wemo WIFI Insight UK switches which have been working perfectly for the past 6 years with the v2 Hub (US frequency).

But in the past month, 3 of them have been going offline completely and had to be reset to rejoin Smartthings. This doesn’t look normal. However they are accessible still in Home Assistant (which I started using recently).

I wonder if anyone has experience this? Thank you so much in advance.