Hi there. As a workaround, he can complete this step on a second character where his inventory is not full of Umbral Engrams. This progress is account-wide, so once you unlock the ability to decode them on this second character, you can go back to the original character and turn them in. Otherwise, this is slated to be resolved in the next hotfix. [quote][b]UPCOMING RESOLVED ISSUES[/b] Below is a list of issues that will be resolved with Hotfix 2.9.0.1: • Players will a full engram inventory of Umbral Engrams may be blocked from completing the Season of Arrivals opening quest.[/quote] https://www.bungie.net/en/Explore/Detail/News/49254