WiFi gets disconnected randomly

I bought an HP pavilion laptop in December this year. The laptop came with a intel wireless ac 9560 160 mhz network adapter. Ever since I opened it up, the WiFi was dropping randomly. No specific intervals. Nothing. I put up with it for a while and then this month, I lost it and since the laptop was under warranty I got them to check it out and had the laptop sent to customer support. To give you a little bit of background:

1. Yes, all other devices connected to the WiFi are operational.

2. Yes, I updated all drivers before sending it in. Uninstalled and installed the driver and all that fun stuff.

3. Power management for the adapter was also adjusted.

4. All windows updates were run and updated.

All of this was before sending the laptop in to Customer Care. I got the laptop back last week and they have replaced the network adapter with realtek rtl8822be 802.11ac pcie adapter. And the problem persists.

1. My initial reaction was that there was something wrong with my router - I use a super old one - Netgear router WNR1000v4. But here's the thing:

a. My 10 year old laptop and all other devices connected to it seem to work OK.

b. My work laptop which I'm using WFH also connects to the same router just OK. I will have to admit that I have randomly lost WiFi on the work laptop as well but much much much lesser times than I have on my personal one. That is also an HP laptop but with an intel network adapter.

The problem with the current adapter seems to be two fold: the internet will slow down randomly (not shut off) but will shut off and become absolute shit when I disconnect the power supply and run off of a battery. Yes, I have already adjusted the power management to use the max performance on battery for the wifi adapter.

I am considering buying a new router before getting back to the customer support but I was wondering if there is something that I'm missing.