In 1.9+ clients, a chunk only renders if the chunk N S E and W of the current chunk are loaded. 1.8 does not do this normally, so the client is not sent any empty chunks around this. With multiconnect translating from 1.8 protocol, the 1.8 server does not send those empty chunks around a chunk, so the client does not render the chunk.
Source:

The fix:

• The workaround is to load the chunks with blank chunks, and even if you load the chunk with a blank chunk, the next chunk packet will overwrite the blank one
• Init the chunks NSE&W directly

Source:

Thanks to Lizard for helping us avoid a debugging nightmare and explaining what's causing the problem and how it could be fixed!

Does this still occur on the latest version?

I've got this on bridger.land