If you are trying to increase your weapon damage (e.g.) from its robust to its infused value, all you need to do is transmute the piece from robust to infused. You do not need to (and actually cannot) reapply the same glyph to see the increase. There is no “robust glyph” vs. “infused glyph.”
If that’s not what you’re trying to do, can you give us some more specifics? What glyph did the piece start with? And what are you trying to change it to?
I've just checked all my Briarheart, Spriggan's, and Agility jewelry (some purple, some gold, some bound, some not, some transmuted, some not, but all with gold-level enchants), and they're all behaving as expected: anything with an enchantment other than gold-level weapon damage can be overwritten with a gold-level weapon damage enchantment, while the only ones that refuse to take the weapon damage glyph are the ones that already had that exact weapon damage glyph applied.
If you're sure that the items didn't start off with the enchantment you're trying to use (if you got them off a guild trader, keep in mind that the seller may have changed the glyphs before listing), then the best I can suggest is to submit a /bug report with screenshots.
You might want to post a screenshot of your issue, @Lohworm.
Because you can re-apply a different enchantment to gold jewelry an unlimited amount of times ... providing the glyph you're applying is CP160 appropriate level.
Similarly, you can transmute the trait on gold jewelry an unlimited amount of times.