Although the OnePlus 5 and 5T are three-year-old phones, the stream of software updates hasn't been cut yet. In fact, there's a relatively big update coming to both of these phones, but there's a hold up on OnePlus' side. The company explains why in a post in the community forum. The OxygenOS Product Lead has opened up about the delay saying that there's a big issue with the communication module. Moreover, OnePlus isn't able to solve this by itself, so it has to reach out to carriers, collaborate and squash the bug. The product team's highest priority right now is pushing the OnePlus 5...
Source: https://www.gsmarena.com/oneplus_with_official_statement_why_the_5_and_5ts_update_has_been_delayed-news-45381.php