Suggestion for Wi-Fi Extender/Repeaters

Hello,

Please suggest Wi-Fi Repeater for my home setup as follows:

1) Airtel V-Fiber 40 Mbps Plan provided with D-Link DSL-224
2) 3 BHK DDA Flat with Router placed in Drawing Room but coverage, not that good throughout.
3) Using a Xiaomi Mi Router 3C as Wi-Fi Repeater but it is not reliable or able to maintain a stable connection.

Brief History: I was facing connectivity issues for quite some time on my old ADSL Connection wherein the DSL light would disappear frequently. On one of the engineer visit, I got to know about V-Fiber availability and upgraded to that but connection remained intermittent. After several escalations/engineer visits, the home wiring was changed and now, connection to D-Link DSL-224 from Airtel is stable, but Xiaomi still keeps things intermittent. Now that I have got the connection checked from exchange till my router with new cabling plus observed main router behavior, I believe it is the Xiaomi at fault now for intermittent Wi-Fi.

Please suggest some alternatives or anything that can help me in maintaining a stable and reliable wireless connectivity with coverage throughout my home which was the case before 2017. Using Airtel since 2007 though,

Thanks,