Testing for custom item tags

I was using McTsts's Encer Chest GUI datapack (https://github.com/McTsts/Ender-Chest-GUI) for a project that I've recently started working on again. Due to the age of the project, I've needed to update everything with the changes to commands from ~1.19.3-1.21 After fixing all the actual errors thrown when trying to load the datapacks in the world, the ender chest guis aren't functioning properly, but I believe I've narrowed it down to this line: execute unless data entity @s EnderItems[0].tag{egui:1} run function egui:gui/code/restore The conditional always evaluates as false, despite not doing so in the past (a couple of years ago). What has changed since 1.19?