To reproduce the error, you need to create an object and make it usable. In the workflow, put the delay function first, and the next speech: player

Test on: 9.0.2.37176

Export code to test:

!DkvZUTjqq4NL(a04LLajY3Wqoyj7fhpar5YuWMv2irWrW6O6lwkjxYJqEmQuvFpmVrzMLuPMkLlraZo7mmFFZFOdMGkh6vi9rLebH0ri89CKEUbtUngvU0FatvK0GqYTKoDhczR7As70ScKWsglqpaiPvvIq39A96T)4(6Id6wekA30n4hg1zPR)Pt)P)X(NiW5hGERR6izdcs2G7xa0zAZXCZw9X8Y2In7AoMVExt3(7idh2T)B)pxgMkgBlgeecekTarEk1eniS2EVHZhZFJVuBkQQ7g6mZJyicJO2GyKqos6Cmx4p2ZzS0JSpbHtV2)s)ZN(9PF99GhQkAkwUaHmu57snWpZ)SyQ6jANtNk6ZK9(SckZiQo7Ck2pY5fJ9UySRpNtHXCofpfxraCJTUIsTh08d4qNIG3pzLLKchsNE9(2kZHz6h018WhMeWGC9vmiHjS86aBJAraF5gRCbqMCUKsRSalbHlzZPasfwe7ukiSsv2iP8ALTMjPk4Fwc4fjgZRymm24hw2EFvJB7QZhQBdIV9

The error shown by BugGrabber:

1x [ADDON_ACTION_BLOCKED] Modification 'totalRP3_Extended' tried to call protected function 'UNKNOWN ()'.
[string "@! BugGrabber \ BugGrabber.lua"]: 519: in function <! BugGrabber \ BugGrabber.lua: 519>
[string "= [C]"]:?
[string "= [C]"]:?
[string "= [C]"]: in function SendChatMessage ' [string "@ totalRP3_Extended \ script \ script_effects.lua"]: 168: in function method '
[string "@ totalRP3_Extended \ script \ script_generation.lua"]: 94: in function
<... ddOns \ totalRP3_Extended \ script \ script_generation.lua: 87>
[string "Generated code"]: 11: in function <[string "Generated code"]: 10>

I'll leave the ticket open as a reminder to put in a better warning, but this behaviour is intended by Blizzard since 8.2.5. Chat messages can only be sent instantly upon a mouse click/key press (except for emotes if that hasn't been changed already).

In this case, can you tell me which API the change occurred in?

https://wow.gamepedia.com/API_SendChatMessage

Patch 8.2.5 (2019-09-24): Including Patch 1.13.3; Partially protected; "SAY", "YELL" and "CHANNEL" must be triggered by a hardware event

Note that the restriction only applies when outdoors for SAY/YELL channels - instanced content such as garrisons should still work.