Impossible to tell without more information - wall height, present condition, original construction, provisions for darinage, etc.

If the wall is holding back a slope, wooden posts are unlikely to provide enough support.

First, you have to look at your survey to determine who owns the wall. If the property line is on the dirt side, then you own the wall and he owns the dirt. That means the headaches are all yours. (Or vice versa) If the property line is down the middle of the wall, then you both own it and need to maintain it properly. Half assery with wooden posts isn't proper repair and maintenance.

Retaining block walls hold back a LOT of weight. If damaged or improperly constructed, a heavy rain can cause them to move downhill and carry the hill with them. Y'all had better have deep pockets, because you are assuming the liability if it fails. Insurance won't pay for damages due to neglected maintenance or improper repairs.

Can you post a picture of the wall please? That will be more helpful to understand the situation.

Here is a link that might be useful: Handyman London

Cinder blocks or concrete blocks?

After 1971 quake in San Fernando area my dad talked to man that was really upset about his very long wall & how much it would cost to repair or replace it. Since it was on level ground & just a foot in on his property from sidewalk my dad drew him pilasters to put up every 8-10 ft. They are cement wider at bottom & have rebar in center & are up against side of wall that was leaning out toward street. Wall was only leaning not broken anywhere.At top the cement is narrowed. Looks like it was meant to be that way. I drove by it yesterday & it is still in great shape. About 200 ft. long. He mixed cement up himself after dad helped him brace it with 2x4's once pilasters were cured all braces removed & looks like it is all original. The cement was just smoothed& is narrower both ways at top so from side it is narrower than at bottom & looking straight on it is narrower as goes up. I think dad had him dig down about a foot to embed the rebar, can't remember is dad made him a form or not. Dad is 95 now & had stroke so wouldn't remember but the man saved a lot of money & since it is on a corner it was all his responsibility. No neighbor to deal with. Good luck. Oh, wood rots so cement would be better. If fence in good shape might be able to sink steel poles in next to it but wouldn't look professional like 1 my dad helped guy do.(At no charge I might add).

The point about being sure of who owns the problems is a valid one. If you turn out to be the owner, be sure to check with your city about any permits needed. Retaining walls over 16" need a permit for replacement where I am and I imagine it's not too different in most locations. Ones over a certain height also have to have an engineer's stamp in addition to a permit. Wet soil is a lot more heavy than you imagine, and doing an incorrect fix on a tall retaining wall is potential disaster in the making. Just look at the film footage of a mud slide to get an idea of the power of wet soil and gravity.

My answer is No. Wooden post is not suitable to support the wall. Temporary Yes. If you set wooden concrete post in the concrete it will root very quickly.

You can call London Builders to get more information