Line dropping at regular time ??

[#1]

On Tuesday and Wednesday and Thursday (today) this week, my internet connection dropped at about 3pm.
On Tuesday and Wednesday this week, it also dropped at about 4pm too ...
Is there something happening at 3 and 4pm that could cause this ?
I should also say it's been dropping at other times, but the 3 & 4 pm on successive days seems an unlikely coincidence.  Can my line be checked please ?
A bit of background ... My Outlook checks for emails every 3 minutes.  Over the past couple of months I've noticed an Outlook popup asking for my username and password ie it couldn't check the mail.  As they became more frequent, I eventually decided I ought to consider replacing my Openreach modem and Netgear WNR1000v2 router.  (There are no firmware updates for it any more - it's 3½ years old) 
I have a new TP-Link VR900 "on test".  It's worse !  The Netgear reconnects so quickly, the only thing obvious sign is the Outlook popup.  With the VR900, it takes minutes to reconnect and perhaps a few reboots, which is hopeless in this situation. 
Today, I'm using the VR900 as the modem with the Netgear router.  The only thing I've noticed is the Netgear log shows 2 line drops.  Later, I'll see if there is a matching log on the VR900 for the modem.
However, these Outlook popups have been more frequent for perhaps several weeks.  So that means it happens with
a) Openreach modem and Netgear router (most of the several weeks)
b) TP-Link VR900 (brand new, but could be going back) (about 10 very irritating days)
c) VR900 & Netgear WNR1000v2  (today)
so is there a problem with the line ?
This evening I'll report back to TP-Link support, but it would be good to hear
a) if there is or isn't a problem on my line and
b) IF ANYONE ELSE HAS LINE DROPS AT 3PM AND / OR 4PM ...  and if anyone can think of a reason for these times, that could be interesting too ...

[#2]

Just for starters:

Electrical noise from external sources, say a nearby premise has a lit sign or lots of external Xmas decorations and they switch it on at 3 or 4pm?
Or your household heating system turns on and generates electrical noise onto the house ring main?

[#3]

@ georgelnx
We don't have outside christmas lights - we're a miserable bunch ...
We don't have any christmas lights at all at the moment, and when we do, there'll be nothing automatic about them.

The central heating is off all day and certainly off at 3pm.  The times - and there have been drops at various times - don't ring a bell.
There isn't anything that I can think of in the house or nearby.  Really, I was asking if anything happens at Plusnet at 3 or 4 pm ...

[#4]

The Outlook pop-ups could be a red herring.
If the pop-up appears immediately ping one of the popular sites, both by name & IP address, you're checking to see if the Internet is actually down.
Check the modem or router logs to see if there's disconnect time match.
Have you another wired PC you could try ?
I reckon if there was a PlusNet problem each afternoon your post wouldn't be the only one.
DM

[#5]

@ Champnet
There are other PCs, but this is the only one with Outlook permanently running.
My router's log shows a disconnect for 1½ minutes at about 20:25 this evening.  I was on the internet and didn't even notice ...  The log also showed a disconnect at 3pm today.
If Outlook had tried at the wrong time and didn't wait long enough, I guess the popup could appear.
On the previous two days the VR900 was both modem and router and it clearly lost connection at 3 and 4pm - and had logs to match.
So there are definitely occasional glitches in the connection at various times - it's just that 3 and 4 pm seemed to be repeats. 
The disconnections really upset the TP-Link when it is acting as router, but don't seem to upset the Netgear router unduly, so these glitches could have been going on for a long time without my knowing.
Thanks for the feedback

[#6]

Could my line be checked because I've been getting brief line drops for days ?

[#7]

Moderator's Note
Topics merged.