I think this happens to you because of the performance limit of 31 highlights per client.
You’ll need to destroy an older highlight in order to display a new one. (Disabling it will still add into the 31, that’s why you need to destroy it)
You can read about it here: Highlighting Objects | Documentation - Roblox Creator Hub
Any chance for Highlights to finally get a thickness property? I believe highlights already support some sort of editable thickness property since studio itself already allows for that behavior, no? So why not add that as a property to the highlight instance as well?
Can we see anti aliasing and thickness available on higher end devices?
Will the highlight limit ever be removed?
Could there be an expansion for a highlight amount limit in the future?
It would be possible for desktop highlights. Mobile highlight, while looking the same, use a novel in house developed algorithm that is super fast, but does not support thicknesses.
So then what does studio use for its highlights in order to support a thickness property?
We may consider it if there is a bigger push from the community. Not only that we can theoretically remove it, but we could change the limit to be per highlight visible on the screen and not per highlight in the workspace. That would more or less have the same performance cost as current system. This depends on our dev community. If you guys will let us know that you really need it, like you did with mobile outlines, we will allocate time to make these changes.
Highlights, while looking like a simple feature can be quite performance heavy and changes to the system needs a lot of consideration and engineering time
It uses the same system is client. I’ve said that thickness is possible on desktop and studio is only on desktop (PC/mac). Thickness changes are only possible on desktop. On mobile we use completely new technology that is heavily optimized and does not support thickness changes.
Yes that is a simple fix that we are planning on rolling out. Flip side of the coin is that some people rely on this bug.
Very glad this update finally happened and I hope it will never roll back! But I have one question, will there ever be a property (say displayOrder/ZIndex) which is only available when the occlusion mode is Always on top? Its purpose would be to decide which would render above the other highlight first, this can be very useful especially for specific effects.
We do need! I never understood the 31-32 limit for highlights especially with how strict it is. Personally i never understand any limit to any of the features you guys add and just seem entirely redundant and a waste of resources from your side. Yeah there’s probably some developers that don’t know any better but ultimately it should be up to THEM!
Many people wish for the limit to be removed completely, a screen-only limit is the exact opposite of what we want. You could just remove the limit completely and let the people figure out how many highlights they are going to put in their game, which will allow you guys to improve upon the system’s performance with less pressure since the limit is currently the only thing that makes highlights unattractive.
Edit: By the way, is there also a way to have our suggestions heard out more clearly? I feel like there are a lot of great suggestions out there that either get overshadowed or simply ignored.
Oh my god! Truly amazing, and well-needed in the community as well! Step in the right direction Roblox!
Looking awesome 
Hope you guys add more awesome features for mobile in the future!!
What’d be great to have a lesser impact on perfomance, is to add material configuration. Stuff such as (an example) selfillium 1 on a glowing texture instead of relying on neon parts. Unreal Engine 2004 and Source Engine already has this, why not roblox?
In all likelihood this is technologically impossible. 31 is 1 off from 32, which is a power of two - Roblox likely reserves one highlight layer for core UI so I imagine the limitation here is that they can only allocate 32 of a certain resource under the hood. So it’s not about choice but computer limitations.
Man, I have been waiting for this for far too long, and they finally delivered.
I’m going to highlight everything in my game right now because there isn’t an excuse not to anymore, lmao.
Yeah, and when will we have anti-aliasing for our highlights? You think it should be mandatory from the start, right?
To be honest, I find it strange that it has not been added in over two years.
Man, i know, we all know. I just believe having arbitrary limitations is dumb and a waste of time on the side of the actual engineers. The lack of any arbitrary limitations could potentially help developers make better games and also help newer developers understand why optimization is good.
32 layers is my guess for this limitation.