Consider the Heiban verb やる. According to a video on Japanese verb pitch accent rules, Heiban verbs with no downsteps remain Heiban when conjugated to their negative form. Prosody confirms this rule with やらない:
But if I add a か particle after it, it completely changes the pitch pattern detected:
Is this a mistake with Prosody, or can clause ending particles like か (and others like ね, な, の, etc) affect the pitch of the verbs before them?

