Forward drive not engaging properly

I have a 2007 Discovery 3 HSE auto. For the past couple of weeks I've noticed that I sometimes lose forward drive and have to pull the change lever back to re-engage even though it seems to be in the correct position. Has been getting slowly worse. Today I had to hold the change lever back against its stop all the time when driving otherwise the box went into neutral. Neutral, Reverse and Park are all operating at the correct point. Is a slight adjustment required to the operating lever linkage the most likely solution? If so, how do I access the adjustment. If not, any other thoughts? No error messages are being displayed.
thanks
Edward

Siezed gear selector bush on gearbox.

Parts are about £3 and a 5minute job to fit.

Thanks Vissie

I'll take a look tomorrow!
Edward

Dismantled the gear selector bush, cleaned and lubricated it. Now my problem is resolved.
Many thanks Vissie!

Edward