B1 b2 - 221 g

[tired_chandra]

My dad has visited the US multiple times on B1/B2 visa in the last 10 years, however he went for a renewal in April and his case has been stuck in 221G for six months now. It was a drop box and he was issued a 221 G within a week. He had his B1/B2 visa valid until the end of September but they canceled the existing stamping and put his case under 221G.He was given a blue slip. He was asked to submit additional documents like salary slip, resume and invitation letter via email which he did. Then they sent another email asking to drop the documents in person which he also did. After that he has heard nothing on the case. By logging into his case on USCIS website, all it says is that the last action was in June. We recently submitted a service request and we were told that the candidate did not submit documents and that is why the case is on hold which is not true because we do have an acknowledgment email stating the documents were received. However we did submit the documents again via email a month ago and haven't heard anything again. We submitted two more service requests which they are required to respond within 2 days but we havent recieved any response in the last 2 weeks.

How long should we wait and how can we help this situation. Anybody has any advice or recommendations?