I'm hitting exactly the same issue. Download speed shows 30~55 Mbps where upload speed hits barely 2 Mbps. In some tests, it shows less than 1 Mbps. I had the same issue last week and then rebooted the router that ran me 3/4 days and hitting again the same issue.
I can imagine seeing much lower than expected upload speeds would come as a shock to say the least! We'd be happy to assist in getting to the bottom of this for you. Would you be able to follow the recommendations for troubleshooting slow speed on our Knowledge Base here?
Feel free to post your results here as well (ensuring no personal information is visible including IP/MAC addresses).
Looking forward to identifying and resolving this slow upload speed issue with you. Keep us posted!
Thanks for your response. I have reviewed the DocsisWAN data of my router and compared it with that knowledgebase. Also, I got a download speed of 93 Mbps and upload 16 Mbps in the speed test. Please let me know if this gives any indication of my issue.