The latest situation. I talked to Apple support and they noticed that the IPv4 address on my airport extreme was not my external IP address but a local network address. I phoned my ISP to get it fixed but they broke it completely so I was without internet for three days. An engineer came and fixed the problem.
Still I could not connect to profile manager or wiki. However, this coincided with an operating system and server update.
Now I can connect to wiki and profile manager, all data still present BUT the original annoying problem is still there with messages every 4 seconds.
Access Log (Service Proxy)
server.bowring.onl "127.0.0.1" 127.0.0.1 - - [22/May/2016:08:42:26 +0100] "GET /devicemanagement/status?auto HTTP/1.1" 200 1236 "-" "devicemgrd (unknown version) CFNetwork/760.5.1 Darwin/15.5.0 (x86_64)"
Error Log (Service Proxy)
[Sun May 22 08:43:43.197406 2016] [authz_core:debug] [pid 35997] mod_authz_core.c(806): [client 127.0.0.1:59073] AH01626: authorization result of Require all denied: denied
[Sun May 22 08:43:43.197486 2016] [authz_core:debug] [pid 35997] mod_authz_core.c(806): [client 127.0.0.1:59073] AH01626: authorization result of Require ip 127.0.0.1: granted
[Sun May 22 08:43:43.197489 2016] [authz_core:debug] [pid 35997] mod_authz_core.c(806): [client 127.0.0.1:59073] AH01626: authorization result of <RequireAny>: granted
[Sun May 22 08:43:43.197500 2016] [:debug] [pid 35997] mod_hfs_apple2.c(363): [client 127.0.0.1:59073] mod_hfs_apple: compare_paths /Library/Server/Web/Data/Sites/Default/ vs /var/empty/devicemanagement/, related=0
[Sun May 22 08:43:43.197503 2016] [:debug] [pid 35997] mod_hfs_apple2.c(363): [client 127.0.0.1:59073] mod_hfs_apple: compare_paths /Applications/Server.app/Contents/ServerRoot/usr/share/web/customerror/ vs /var/empty/devicemanagement/, related=0
[Sun May 22 08:43:43.197506 2016] [:debug] [pid 35997] mod_hfs_apple2.c(363): [client 127.0.0.1:59073] mod_hfs_apple: compare_paths .*\\\\.\\\\.namedfork/ vs /var/empty/devicemanagement/, related=0
[Sun May 22 08:43:43.197509 2016] [:debug] [pid 35997] mod_hfs_apple2.c(372): [client 127.0.0.1:59073] mod_hfs_apple: Allowing access with no matching directory. filename = /var/empty/devicemanagement
[Sun May 22 08:43:43.197658 2016] [socache_shmcb:debug] [pid 35997] mod_socache_shmcb.c(584): [client 127.0.0.1:59073] AH00840: inside shmcb_status
[Sun May 22 08:43:43.197667 2016] [socache_shmcb:debug] [pid 35997] mod_socache_shmcb.c(673): [client 127.0.0.1:59073] AH00841: leaving shmcb_status
): [client 127.0.0.1:59073] AH01626: authorization result of Require all denied: denied