Bug Description

The current Curse version of Better FPS (1.4.8, released in 2017 [1] on CurseForge for Minecraft 1.12.2) has an issue that has supposedly been fixed on GitHub in 2018 [2] through a pull request.

The bounding box only grows in one direction. I don't know the specifics, something like only top south-east.
Because of it, the beacons' potion effects only apply in that quadrant.
This issue has been present for years as far as I recall and I suppose it affects both clients and servers [1].

I've had the issue some years ago on a server and I've discovered it was still present on a brand new server (latest version, 3.2.1).
I've looked it up on the net and recently found that the option config/betterfps.json::fastBeacon was the culprit [3]. I've then made some more investigations as described above and below.

To see if this would actually fix things, I've gone on a single player world with no modifications and the bug was present there too.
I've then set fastBeacon to false, restarted sevtech and finally after getting to my singleplayer world, the beacon seems to work as expected.

I have messaged the server admin about it, but as of right now I have no results nor any tests of the fix server side.

I'd still suggest to set the default config so it'd disable the fastBeacon option for both servers and clients until Better FPS updates, one day, perhaps.
I apologize that, as of right now, I don't have any tests serverside but only assumptions compared to the singleplayer tests, albeit the references. And I apologize if this template wasn't the right one. Even if it's a request to change a config file, it'd seem silly to put a bug report as a feature request.

[1] https://www.curseforge.com/minecraft/mc-mods/betterfps
[2] Guichaguri/BetterFps@7ea260f
[3] https://www.reddit.com/r/feedthebeast/comments/aqvacs/1122_weird_bug_with_beacons/

Did this behavior use to work in the previous version?

No.

Steps to Reproduce (for bugs)

1. Make a beacon, any layer size from 1 to 4 and activate it with any potion effect
2. One quadrant gives and refreshes the potion effects
3. All other directions won't give nor refresh the potion effects

Hello again!
Just commenting that I've been informed by the server admin since he has changed the config and rebooted the server.
He told me the beacon works for him now! (I just asked him and he didn't have to disable fastBeacon on his client. Even though it shouldn't matter)
I've logged in just now to test a bit (rudimentary tests, I've gone in all directions, above ground, a bit under the beacon y level, in the water, out of line of sight, underground...) and I can confirm it works for me too!