Gigacube 5G router performing poorly vs Mobile 5G (Vodafone) SIM

[Grinds]

Why is Gigacube 5G so prone to dropping performance?

Noticed it for a week now, getting approx 30Mbps download from my cell id 0029a314 yet my iPhone (13 Pro) with a 5G Vodafone SIM is giving me 160Mbps download! 🤔

Switched the SIMs over and the Gigacube SIM in my mobile gives me >300Mbps download and my mobile sim in the Gigacube drops down to 30Mbps. 😣

If I can't solve this myself, I know I'll get told to take this to a shop, who will look at it and not be able to do anything and say they need to send it away... so I'll be without any router for days. 😫

I work in IT BTW so I can pretty much conclusively say its something router based.

[Grinds]

And today in a non-optimum location..  I can get 160Mbps. go figure?

[Grinds]

So this never really recovered. TOBI and then the agent were next to useless - a common frustration when your day job is in IT. I had noted the CellID change to  0029a30a but that has not affected performance - still sub 30Mbps. Whilst working from home had another go.

• Up to date testing. 5G (Talk)Mobile in same location was giving 190Mbps.
• Removed SIM and replaced as recommendation made no difference.
• I resorted to factory reset (which I hate doing because it involves adding back in all my personal config) but performed it nonetheless.

And...

Instantly recovered performance to provide me >220Mbps connected to Cell ID 0029a30e.....But why?

I had this before about 6 months ago, but does anyone have any idea what the reset is actually doing? And how I can avoid the need to do it in future?