In situations like this the choice between past and past-perfect forms depends on where you want to focus your reader's attention.
A cinematic analogy† may help: think of your time references as a sort of temporal 'camera', which can
point at different points along the conventional left-to-right timeline: straight ahead for the present, to the right for the future, or to the left for the past ... and at future or past points that are more or less distant from the present.
employ wider or narrower framing to depict a larger or smaller span of time.
When you employ a past-tense form, you are pointing your camera at a particular point in the past—your 'Reference Time' (RT)—with a relatively narrow framing. In consecutive narrative you pan more or less gradually to the right, so your RT keeps shifting to later and later events.
But if at some point in this narrative you employ a past-perfect construction, you abruptly widen your frame to include not only the events at RT but also events before RT. These prior events are more distant, so they lie to the side or in the background of your frame; events in your 'current' RT are still focal, foregrounded.
At this point, however, you have a choice: you may maintain this perspective, with its foreground/background contrast by continuing to speak in the past-perfect, or you may shift your perspective—narrow your frame and redirect the camera to the prior events—by continuing with past-tense forms.
There's no rule in grammar which says you "should" pick one or the other; it's an artistic choice.
† The same analogy is employed in §4. When and how should I use the perfect? of our Canonical Post on perfect constructions, where the time-shifting use of perfects is addressed more fully. I may say that the analogy is not my own; I encountered it ten or fifteen years ago on the old B-Hebrew list, in discussions of the verb system in Biblical Hebrew.