Nice that the o2 solved most your issues. Always important to eliminate other causes for possible trans problems first.

Change the fluid, rubber seals, and service with Valvoline MaxLife multivehicle. DO NOT USE ZF LG6! LG 6 should only be used on a vehicle that has had regular maintenance. I'm one of the few who have experience with LG 6 on high mileage, not serviced, transmissions (multiple vehicles). Do not use ZF fluid. It's a waste of money and is thin resulting in not maintaining pressures.

That said, at your mileage, as others have said, changing fluid (or not changing fluid) may result in blaming a fluid change for trans errors or other erratic behavior. No way of telling. At your mileage with no service history your trans is a time bomb. If keeping the vehicle, prepare for a trans change financially.

Were it mine. Change with Valvoline fluid, not flush, just drain and fill. Replace bridge, tube, pan/filter, and mech seals. Good luck.

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2005 X5 4.4i Build 04/05 Maintenance/Build Log
Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles)

2006 X5 4.8is Build 11/05 Maintenance/Build Log
Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles)

2010 X5 35d Build 02/10
Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles)