Have you performed isolation testing?
Performed isolation testing (with and without Better Combat, since these two mods typically go hand in hand and are often installed together) on version 2.2.4+1.21.1, which I believe to be the latest version.

Describe the bug
Star's Edge's active ability grants the player Speed II on the first activation, and grants both Resistance III and Haste VII on the second activation - all three effects being effects beacons can grant as well. If the player activates that weapon's ability while one of its effects is also being granted by a nearby beacon, this causes the ability to behave in unusual ways.

To Reproduce

1. Enter a creative world and build a beacon. Power it, and choose Haste as the given effect. The beacon will periodically grant nearby players Haste I for 9 (or more, depending on the beacon's level) seconds at a time, as expected.
2. While under the Beacon's effect, use the active ability of Star's Edge in order to grant Haste VII.
3. Open the menu to see the Haste effect's duration.
4. The Haste VII effect will last for however long the beacon's haste had remaining, and will persist at level VII for the full duration. For example, if you had eight seconds of Haste VII remaining when you used the weapon's ability, you would have Haste VII for eight seconds.

This works with the weapon's Resistance effect as well, causing a similar extended duration effect. However, under a Speed beacon, the weapon's active ability becomes unusable entirely.

Expected behavior
Using Star's Edge's active ability normally only grants its buffs for three seconds (five in the case of Speed), so expected behavior is (presumably) that in a beacon's area of effect, the Haste effect would only exist at level VII for three seconds, and once that expires, the player would have Haste at the level granted by the beacon for however much time was remaining of that Haste effect.

Additional Info:

• Modloader: Fabric
• Modloader Version: 0.17.2
• Minecraft Version: 1.21.1
• Mod Version: 2.2.4 + 1.21.1
• Environment: Singleplayer

Additional context
I've tested this with a couple other weapons that grant these effects (Twisted Blade and Storm's Edge specifically) and both seem to behave normally while under the effects of a nearby beacon. As of writing I have not tested on Forge.