It might be worth checking with an older version to test your theory. If you want to try a particular version of Opus and need the old installer, let me know which version you want to test.
You may also find the same problem happens with the old version, even though it didn't before.
The larger memory leaks are often (not always, of course) caused by shell extensions something else has installed/updated, which get loaded by Opus and attributed to dopus.exe (and other programs that load them) in Task Manager.
There's a tool which can be used to diagnose where a leak is coming from. If it's in Opus, that will help us locate what needs fixing, and if it looks like it's another piece of software then it can be reported to them, or may just reveal which thing needs updating and has a fix already.
It's a fairly technical tool, but we have a step-by-step guide on what to do (although we don't expect it to make sense to everyone):