Thats the problem with technology.
Troubleshooting the issue may or may not be easy depending abit on luck I would say. Sometime the issue might not shows up in the first try troubleshooting that whys usually IT staff will have to go thru the same process over and over again. At times it happened on x number of tries.
To put it simply, for example a simple case of no connection, looking at consumer point of view would be, ok no connection, must be the relavant ISP issue, but on the other end, this issue might be cause by:
-Product receiving connection (eg. Laptop / Desktop) which also got to repeat the same troubleshooting for both firmware/ hardware issue on the device.
further to that, at time theres also issue with the cabling work (eg. your fibre point connection patched properly?)
Thats why theres an SOP for all technical staff to strictly follow.
Anyway, since you've tried flashing the latest firmware. Just observe it for the time being.
Nice! Hopefully you will not have any further issue on the internet which can be pretty irritating at times. haha!
Look at the speed? Not bad.. but again this is what i mean, with no changes to the hardware, speed variates. I can understand that its shared bandwidth and time of day, but not to the extent of dropping below 100Mbit.. then be asked all kinds again, wired or wireless, maybe your cables spoil, reset router, reset ONT, plug direct to ONT what speed haha.. yes I know its SOP, but I think whats important here is SLA for speed providence, dropping to below 100Mbit is abit weird.
Speed indicated is via 868L with FW:1.09 that was manually flashed on to the EOL router that was given to me. Wish my ASUS AC68 can be used instead.. (maxes at 500Mbit), when I am facing 100Mbit saga.
As per what @razerpro mentioned, best is to test using direct connection with ONT to ensure accuracy. Every device or equipment in between the connection will only varies the result.
@Benedict1972 Bro, Testing via direct connection to ONT will allows the technician to know if the issue lies with the connection or the router.