All very interesting to hear, and understandable that it's a curious problem. Again, perhaps others will have more to share as answers. For now, I have still a couple more questions to try to help diagnose the situation.
So about what you are setting as that loadpath, you say in this last reply that "I am setting [...] my loadpaths to my single directory "D:\ColdFusion2021\sandbox\wwwroot\asp\package\java_lib"". First, can you confirm you are setting that as a hard-coded string? Or is the path being set from a variable? If the latter, are you dumping the value of that variable in your try/catch?
Second, you had said originally that "I'd like to allow each subdirectory to have its own "java_lib" folder with jar files, and to set this.javasettings.loadPaths in each subdirectory/Application.cfc". Given the path you show, D:\ColdFusion2021\sandbox\wwwroot\asp\package\java_lib, does that mean that this app is using that asp folder and some other app would use a different subfolder of that wwwroot? Of course it's not important WHAT the folder is, and this may not be germaine to the problem. I'm just connecting dots, as we try to understand your issue.
Finally, yes, while Lucee adds a feature on createobect/cfobject to name the library path from which to load that specific class, CF has not yet adopted that. We have only this app-level setting, for now (added in CF10).
I doubt more than a couple percent of CF (or Lucee) users do their own loading of java classes--or with an interest in controlling that at an app (as both CF and Lucee offer) or at the template level (as Lucee offers). I mention this both to propose why CF has not yet adopted that last feature.
But it also explains why there's no means in CFML (I know of) to do the reload you seek, and why there would be few people who would know of this problem and how to solve it.
If you don't get anywhere here, you may want to open a bug in tracker.adobe.com (Adobe folks respond in SOME forum threads here, but not most). You might also want to broaden your reach to the CFML Slack, the Facebook CF Programmers Group, and elsewhere, as there are fans of each who are active only there and not here. I list links for those in a catagory of my cf411 page, specifically at https://cf411.com/cfcommhelp.
If you may get a solution somewhere, I hope you may come back and update this thread here.
Hi. Just an update for future googlers.
The issue was intermittent and I was unable to identify when it worked and when it did not.
I ended up copying the JAR to CFHOME/lib to get rid of the problem.
Not having the source code of ColdFusion makes it difficult to diagnose the root cause so I gave up on this unfrequent scenario in favor of the more traditional approach.
Thank @Charlie Arehart and @BKBK for your help.