Hi there,
I'm running OpenWrt 23.05.4 r24012-d8dd03c46f / LuCI openwrt-23.05 branch git-24.212.79335-cdbe903 on a J4125 based MiniPC as router.
I changed my old router (R7800) from dd-wrt to openwrt as an dumb AP and exchanged the 3 old WR841ND APs with AX3000T. These dumb APs are running Snapshot builds of Openwrt.
I set up AdGuard, 3 VLANs (LAN, IOT, GUEST), Dawn
Now to my problem:
The Setup page for the luci-app-statistics is not opening, I'm only getting an "Error" message (see picture)
The luci-app-statisics was installed quite early in my learning process and was working and is still collecting data. But I afterwards changed the config quite a bit (VLANs, added the APs to my network) an never bothered with the statistics. Today I wanted to integrate some data points to my home assistant instance an looked again in the statistics. I then realized that the setup is not opening.
I reinstalled the packages multiple times, first only via the package manager and in the second reinstall 'run' I also deleted the luci_statistics and collected.conf via ssh with no change in outcome.
I also installed the luci-app-statisics on one of the APs, where it was never installed at all, also getting the same error.
Then because the snapshot was around 3 weeks old I updated to the latest snapshot on another AX3000T, installed luci-app-statisics, same error 
I searched the net and this forum without any result.
Some hints what could be the problem is welcome, if you need additional information just ask for it.
EDIT:
Following error message occurs when I uninstall luci-app-statistics with the packet manager in luci:
Command failed: ubus call service delete { "name": "collectd" } (Not found)
Collected errors:
* pkg_run_script: Internal error: luci-app-statistics has a NULL tmp_unpack_dir.
* opkg_remove_pkg: not removing package "luci-app-statistics", prerm script failed
Thanks in advance
EDIT2:
SOLUTION
After setting up an raspberry pi 3 and installed luci-app-statistics and tested the collectd-Setuppage working I replicated my router config on the rpi step by step to find the problem where the error lies nothing in openwrt was found.
The only "difference" that was left was that I use the reverse proxy function of my synology nas for all my network devices, which I not have set up for the testing rpi3. Didn't expect the problem lies here, b/c I'm using the reverse proxy for a long time now, everything in openwrt was working. But after I used the IPv4 adress to login to my router I could open the collectd-Setup page without issues...
Open point
Why is only (from the packages I use) the Setup page affected? And why is the Error in the first EDIT present?