Kafka Streams with suppress() reprocessing changelog - apache-kafka-streams

Question

I have a Spring Cloud Stream (Kafka Streams version 2.1) application with a Kafka Streams binder and I am doing time window aggregations, where I only want to make some action (API call) once
the window closes. The behavior I'm observing is that on every application restart, my mapValues function is called for every record stored in the changelog,
resulting in huge number of calls being made to the API.
My understanding of suppress() is that for every closed time window, a tombstone record should be sent to the aggregate changelog topic, effectively preventing me from reprocessing it, even after application restarts.
What could be causing messages to be reprocessed on an app restart?
I've already confirmed that the app is not reconsuming the source topic.
Snippet of the relevant code below:
Serde<Aggregator> aggregatorSerde = new JsonSerde<>(Aggregator.class, objectMapper);
Materialized<String, TriggerAggregator, WindowStore<Bytes, byte[]>> stateStore = Materialized.<String, Aggregator, WindowStore<Bytes, byte[]>>
with(Serdes.String(), aggregatorSerde);
KTable<Windowed<String>, List<Event>> windowedEventKTable = inputKStream
.groupByKey()
.windowedBy(TimeWindows.of(Duration.ofSeconds(30)).grace(Duration.ofSeconds(5))
.aggregate(Aggregator::new, ((key, value, aggregate) -> aggregate.aggregate(value)), stateStore)
.suppress(Suppressed.untilWindowCloses(Suppressed.BufferConfig.unbounded()).withName(supressStoreName))
.mapValues((windowedKey, groupedTriggerAggregator) -> {//code here returning a list})
.toStream((k,v) -> k.key())
.flatMapValues((readOnlyKey, value) -> value);