It is possible that the proxy is caching certain elements because even if the 'disk' caching feature is disabled, the proxy still has a memory storage area.
This memory storage, called 'Memory Cache', allows the proxy (only for HTTP protocol) to save certain elements.
However, the memory cache is very small (about 250MB to 1GB).
It only allows the proxy to cache small-sized elements.
Nevertheless, it is sufficient to cache API or application results
If this is the case, the simplest method to eliminate this behavior is to reduce the size of this memory cache to the lowest possible value.
your Proxy > Global Settings
click on the Central Memory link