When a replaceitem command in block mode is put into a repeating command block, sometimes it says "component list parsing failed" but I didn't even use components. I am 100% sure I didn't mess up the command and it's really annoying.
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Cleaning up old tickets: This ticket has not been updated recently (~1 year+) so is being closed as Cannot Reproduce. If you feel this is still a valid issue then please comment, or create a new ticket following the Issue Guidelines.
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Components are used in behavior packs, so this suggests you have a problem in a behavior pack. The "vanilla" behavior pack is built into the game, but if there was a bug in that we would probably have a lot of reports like this, and as far as I know this is the only one. So it's most likely some behavior pack that was added to your world. Since mashup packs and imported worlds can import behavior packs they require, you may not even know you have one.
Since you're using command blocks, I assume you have the technical knowledge to find out if any behavior packs are installed, in the world or in Global Resources. If not, I can help you find out. Please let us know if you can find any non-vanilla behavior packs.