If the TDS out of the RO membrane is really 109 then you need a new system. With a tap TDS or only 128 your RO only should only be between 3 to 5 maximum.
Try disconnecting the line between the RO membrane and the DI at the DI end then make water for at least 20-30 minutes before testing the RO TDS again. If it is still higher than say 5 I would toss what you have and start over with a true reef quality RO/DI for around $125. It will cost you more than that to replace the filters, membrane. flow restrictor and DI in what you have with high quality, low micron replacements.
A reef quality RO/DI will have clear filter housings, no lager than a 1 micron near absolute rated sediment filter, a 0.5, 0.6 or 1 micron extruded carbon block, a Dow Filmtec or equal 75 GPD RO membrane, a capillay tube flow restrictor the end user can adjust, a full size vertical refillable 20 oz DI filter and an inline pressure gauge.