My emails were also ignored before the 6th month but got the PPR in less than 24 hours after my last email to SGVO.Since u r EE then u have timeline 6 months. If more than 6 months, VO has to process as commuter. You did upfront Medical, no need medical request as ours.
For ours as paper based, the timeline is 18 months. Then if we chase VO, they have the right to ignore.
Since you are paper-based and it is stated as 18 months processing time, then patience is the key. All the best to you