PJ here ok.

If only your wifi is affected but not your LAN connection then the answer is obvious.
Maxis router is on leased. Report and they will send a replacement without charge.

morning also ...
morning can't watch youtube and fb clips.
ping can reach 4 digit.

This sounds funny. How can they trace back your neighbour's wifi and came to that conclusion.

I can understand the situation of what you went through just as what I've also experienced similar woes as you the past few days.

My speed dropped to somewhere like 10% of my subscribed speed and pings were like more than 4X higher than normal even when you conduct a speedtest to Maxis's own test server in Subang Jaya.

Called up Maxis Hotline 123 to make a complain about the network fault but was unfortunate to be picked up by a bitchy indian lady on low level support who keeps wanting to blame the problem on my wifi network claiming that it was interfering with my neighbor's wifi signals causing my slowdowns. Keep asking for my router's serial number to do remote tests and all that despite not satisfied with numerous requests asking me to test my line using the Maxis App on my phone.

I told her that as a experienced person who is in this industry how come for the past year I've been using my line without interference issues and isn't it against MCMC's requirement which states that download speeds to the ISP's own server must at least achieve an 80% of subscribed plan speed for FTTH connections? The idiot bitch still keep insisting that it was my local WiFi's fault despite all remote tests got passed trying to down-talk me to make me feel stupid. I was in a good mood that day so I played along until she ask me to restart my router, that was when I took the opportunity to cut off the call since I was calling on a Maxis fixed line using 123.The call ended as soon as I hit the power switch.

Call that bad luck or what, I think our Malaysians telcos now have many untrained rude and frustrated staffs in the midst of the COVID pandemic.Either they are doing it on purpose to make their own company lose customers or they're just passing time just to clock out.

Please consider referring your bad attitude staffs for psychological evaluations or counseling, Maxis. They are giving a bad reputation to your company.  I hope not to switch provider once again once my contract with you ends in a few months time.

Don't get me wrong though and calling me a racists, I've lots of very brilliant and friendly Indian friends out there who are very successful in life today.

Long story cut short...

2nd attempt to call Maxis's hotline. This time I was luckier. A Malay girl picked up the call, though she wasn't fluent in English so I chat with her in Malay instead. Much friendlier tone and helpful though. She wasn't as insisting as the previous rude staff but at least she was helpful enough to ESCALATE the case to higher technical support team and told me to wait on the phone. 

A Malay guy took the call which spoke in a much convincing technical tone seems to know the situation better and proceeded to request that I conduct a speedtest to their local Maxis server 3 times returning the results to them for filing a report with a ticket number and given back to me for future referencing.

True enough within 30 mins after the complain was made, my line returned to normal, I didn't even need to restart my modem and router. I restarted them just to make sure everything was restored properly and it went solved.

My friendly advise to the public is that in the midst of this pandemic, from experience there's no perfect telco company in Malaysia, so try to minimize reliance on them and avoid making your life complicated by subscribing too many services which increases the probability of faults. They're now very pressured with keeping up with revenues with many disgruntled staffs in every one of them.Try to keep your life simple yeah

I took the offer, later the maxis will call n counter u back to retain, so see what u can get. I got only RM20 for 12 months.

Yes, I remembered receiving a promotional call from Maxis about upgrading my line to a higher tiered one just about 1 week back. They seems to be very aware of subscriber's contract ending soon and will keep pushing to get you tied up again by renewing your contract.

Worst there are even cases when a competitor ISPs who would call up and offer you to switch over which makes you wonder how they got access to Maxis's customer accounts.

Don't know if it's true or possible, if you refuse the offer you'll see weird things happening to your line like your fibre modem(ONT) getting miscapped once in a while, line quality deterioration and increased downtimes.

That's why I maintain my dependence on Malaysian telco services as simple as possible.