Game Mechanics: capped at 14 instead of 15 active buffs/debuffs

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I've been running into this weird issue where my character appears to be capped at 14 buffs and no matter what buff I attempt to cast I get a "Your spell did not take hold" message. It's not an issue with spells that don't stack.

Hopefully this picture demonstrates it well. On the left I clearly have 14 buffs and I'm trying to cast ultravision or anything and nothing will take hold. Then in the middle I've tashed myself and instead of taking the empty 15th slot the tash replaces my clarity. It's not a visual bug, I got a message "The soft breeze fades." On the right is an image from another character where I'm not having the issue and I have a maximum of 15 buffs as normal.

https://tinypic.host/image/buffsweird.3qTi6a

And possibly related my buffs are very often switching buff slots when I zone. But my top buff in particular always ends up in a weird spot when I zone. Like in the above picture I probably had jboots in my top slot as a junk buff, but then I zoned. I've tried reloading my UI. I've tried reloading my game. I've tried using a different UI, including an unmodified velious UI. Nothing fixes the main issue or this side issue.

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I should add, obviously I've seen if other players can give me any buff and they can't if I'm at my personal cap of 14.

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I could post a video too if the image is unconvincing.