Yes it seems very inconsistent. However, I was able to figure out a way to make it happen. When I tab out of the game and browse the net or even just go afk. There's a high chance that I'll get error 90002 after a while. I done this while logged on a character on the Chaos Data Center as well as my main character on Primal Data Center, both had the same results of getting error 90002 while I was checking stuff on the net(even while doing this post lol).

Tabbing out and/or having a browser open may be causing this issue in some way, but I've also had this same error while doing stuff in-game. So I'm not certain. There seems to be a way to force it to happen but, I can't explain why I get them whilst doing dungeons and trials.

This is my route to the Primal Data Center with a VPN right after the 90002 error. To me it seems okay.
Code:
|------------------------------------------------------------------------------------------|
|                                      WinMTR statistics                                   |
|                       Host              -   %  | Sent | Recv | Best | Avrg | Wrst | Last |
|------------------------------------------------|------|------|------|------|------|------|
|                            10.254.174.1 -    0 |  100 |  100 |    0 |    0 |    0 |    0 |
|                            10.254.254.1 -    0 |  100 |  100 |  148 |  149 |  152 |  149 |
|                          10.255.250.190 -    0 |  100 |  100 |  149 |  154 |  195 |  150 |
|                              23.92.24.2 -    0 |  100 |  100 |  149 |  152 |  222 |  151 |
|                           173.230.159.0 -    0 |  100 |  100 |  149 |  160 |  218 |  153 |
|ce-0-18-0-1.r02.snjsca04.us.bb.gin.ntt.net -    0 |  100 |  100 |  151 |  156 |  195 |  151 |
|     ae-3.r00.scrmca02.us.bb.gin.ntt.net -    0 |  100 |  100 |  154 |  158 |  202 |  155 |
|xe-0-1-0-1-1.r00.scrmca02.us.ce.gin.ntt.net -    0 |  100 |  100 |  154 |  163 |  301 |  155 |
|                           204.2.229.234 -    0 |  100 |  100 |  154 |  168 |  219 |  155 |
|                            204.2.229.10 -    0 |  100 |  100 |  154 |  159 |  202 |  154 |
|________________________________________________|______|______|______|______|______|______|
But this graph my VPN provides shows a sharp spike in ping at the same moment I got this 90002 error.


Unfortunately, I can't try this on another PC/Laptop etc. Nor can I attempt the phone suggestion.