WiFi Pods 'fair' connection and internet running slow/intermittently dropping

I previously had the Hub 3 and x1 WiFi Pod (white) for 2 years and changed to the Hub 5 and x1 WiFi Pod (white) 9 months ago. The Hub and Pod has been in the same place for almost 3 years, connection status across the Hub and Pod has always shows as 'great' on the Connect App, no changes to the number of devices/usage etc but for the last 2-3 weeks I've been getting low internet speeds (struggling to open browser pages, video calls dropping connection/packets) and intermittent WiFi as well as the WiFi Pod dropping connection.

I contacted VM 2-3 times and was told to reset my Hub and they'll review for 24 hours, which ends in being told my connection is 'great with no issues'. On the last call I requested an additional Pod to see if that makes a difference but it hasn't. I first tried using the new Pod in the exact same place as the previous one but still had the same issues with status showing as 'fair'. I then connected the second Pod in between the Hub and new Pod but still having the same issues but status for both Pods showing as 'fair'.

I'm confused as to why my internet is suddenly struggling despite having the same set up for the last 3 years although now with an additional Pod. The only solution proposed by VM is to upgrade my internet speed (currently have the M350 Volt speed boost) which comes with a 18 month contract extension.

Setup is Hub > Pod 1 in the hallway (next room from the Hub) > Pod 2 at the top of the stairs directly above Pod 1.