Bigguy2017

Those are inputs.

Get a small bag of lock-washers. Switchcraft jacks and CTS pots use washers with 3/8" (9.5mm ish) internal diameter. Lock Washer (Star) for 3/8 Pots and Jacks (pack of 8) Lock Washer For 3/8 Pots and Jacks [STAR(B)] - £2.20 : Axecaster Barrel jacks need 12mm internal diameter Import (metric) jacks and pots are usually smaller. Hosco do wee baggies in all the common sizes,imperial and metric...

You're just after the shown dock bit? You can still charge the transmitter directly with a micro USB cable?

Hmmmm.... If none of the wiring has come adrift it sounds like a pickup problem. Do you have a Multimeter or a soldering iron? With a multimeter measure the resistance across the two outer volume pot lugs - should be around 8K Ohms ish... If it measures around 250K Ohms then the pickup is open circuit. Desolder the pickup lead from the vol pot outer lug and measure the pickup directly - again should be around 8-10K Ohms If no multimeter, desolder both pickup leads at the vol pot and croc lead them to your guitar cable/amp input - if no signal then pickup is open circuit. If you are feeling brave unscrew the pickup (both halves) and pop the covers off. Have a good look at where the cables solder onto the very fine pickup windings - sometimes these break.

Suggestion 2 a strip of ally lager can, superglued into the speaker hole...

40mm Heatshrink sleeving could work Large Heat Shrink Tubing 50mm 35mm 25mm 20mm Various Heatshrink Tube Insulation | eBay

Stage Electric do StageFlex rubber covered flexible mains cable by the metre https://www.stage-electrics.co.uk/View/20532/stageflex-37029-metre-x-bs6500-h07rn-f-rubber-cable-3core-2-5mm-black Also Screwfix https://www.screwfix.com/p/time-3183p-black-3-core-0-75mm-flexible-cable-25m-drum/61627

How are the frets, wear wise - any big dips? Get the fret rocker on it - are there a few high frets - a local level may be all that's needed. If there is meat left on the frets a level, crown, polish is not a big job (takes me an hour and a half, with two mugs of tea)...

Sounds like the ground side is not grounded somewhere... Does it have a ground wire between the pots or does it use the plate for grounding ? - tighten all three pots and the jack onto the plate. Get a croc lead and short the jack ground to a vol pot ground - does that pot now go to zero? Jazz Bass WIRING 01D.pdf

Hmmm... weird one... You've tried all the obvious so it must be something else. Things to try; You could have a weak pickup magnet on the E string (you've changed the pickup so probably not this) - tap all the pole pieces with a (steel) allen key - do they all make a similar bang and are they all similarly 'sticky'? Nut. Have a good look at the nut slot for the E string - is the slot cut right and is there a tiny clearance (try a sheet of paper) over the first fret when string is fretted at fret 3? Also check the E bridge saddle. Room. Are all your listening test being done in the position in the same room? Room dimension s can really effect the low end - my living room has a big peak around A which sounds much louder than it really is. Try with another cable, direct to the amp - there can be odd effects if the cable's conductive plastic layer is not stripped back correctly. (clutching at straws here). What bass, what pickup, what strings? It is possible to wire a PBass or stacked jazz pickup out of phase which makes for a weird response.

Get some bigger Genelecs.

Standard M5 Nylon 66 washer is 5.3mm ID 9.5mm OD 1mm thick - so basically correct https://www.flexibleandfasteners.co.uk/Shop/m5-nylon-metric-plastic-washers/ https://www.amazon.co.uk/M5-Nylon-Washer-Washers-Natural/dp/B006XURJH8 These are nearer M5 x 7.5mm, also nylon... https://www.amazon.co.uk/sourcing-map-Nylon-Washers-Screw/dp/B07NRYZG81 https://www.ebay.co.uk/itm/362586035318

Anyone know what size (ID and OD) they need to be? M4? nylon and PTFE washers are available for pennies...

Rubber O rings might work ?

Possibly a bad solder joint on the neck pickup / pot ?

If Deoxit doesn't fix it then replace the pots.

That size is a Neutrik D-Series - panel has a 24mm hole (also known as Universal Format Connector). M3 countersunk - usually 10mm or 15mm long, plus a plain washer, lock washer and a nut (M3 Nyloc can be used). If doing a lot of them get an M3 nut driver/spinner...

If relief is AOK and minimal check the nut slot heights. Get the fret rocker out... any high frets will ruin a low action. If fret rocker shows high frets then a spot or full fret level is indicated.

I sound a little bit conservative.... Columbus Fender Musicman Aria Rickenbacker EB Musicman Fender Fender Fender Fender Fender

From the picture it looks like all four string slots are 1mm towards the E side - way too much wood showing on the G side. It needs a new nut.