Sharing cache between application and map engine

I'd like to use cache not only to store map tiles, but some additional data of my application. I could create a new cache for that, but obviously it would mean additional buffers (in heap and RMS), so I think it is good to store them together.
Unfortunately it doesn't always work - sometimes it produces "collisions" - my data, particularly images, are replaced with tiles from map.
I do not think it's a result of key collision - I generate my own keys for cache entries, and it's hardly possible MGMap engine uses the same key.
Since the cache is used asynchronously from map engine, and from the app, I wrapped CachingChain with sync code:

public class CommonCache extends CachingChain {

public synchronized void cache(String cacheKey, byte[] data, int cacheLevel) {
super.cache(cacheKey, data, cacheLevel);
}

public synchronized void deinitialize() {
super.deinitialize();
}

public synchronized void initialize() {
super.initialize();
}

public synchronized byte[] get(String cacheKey) {
return super.get(cacheKey);
}

public CommonCache(Cache[] cacheLevels) {
super(cacheLevels);
}

}

but still observe collisions like before syncing, per my observation happening when RMS cache limit is met.

Any suggestions how to fix that are appreciated. I would not like to use separate cache, but at this moment I do not see other way to go :(

Could that happen because of several deinitialize() calls, one from the app and other one from the map engine? Is deinitialize() a sync method, I mean if cache uses separate thread?

TIA,
Mike