ts_headline

I am a bit puzzled by the output of ts_headline (V8.3) for different queries.

I have one record in a test documentation table and am applying different
queries against that table to check out the ts_headline outputs.

The "document" in question has 2553 words which generate 519 tokens in the
ts_vector.
For most queries, ts_headline returns a string starting with one of the
criterion words and with all criterion words highlit - as I would expect.

However, some other queries return a string which seems to always start at the
beginning of the "document" and contains no highlit terms.

It seems that the difference is in the number of occurrences of the criterion
words. If the number of hits is less than some number, the ts_headline result
is "correct" but if the number of hits exceeds that limit, the result is just
the first MinWords of the "document".

I have seen cases with up to 20 hits succeed but cases with 35 hits miss.
The spread of hits does not seem to be relevant.

Is this a bug or am I missing some configuration option?

TIA,
Stephen Davies
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