  Given its large plate scale of 21" / pixel, analyses of data from the TESS
space telescope must be wary of source confusion from blended light curves,
which creates the potential to attribute observed photometric variability to
the wrong astrophysical source. We explore the impact of light curve
contamination on the detection of fast yellow pulsating supergiant (FYPS) stars
as a case study to demonstrate the importance of confirming the source of
detected signals in the TESS pixel data. While some of the FYPS signals have
already been attributed to contamination from nearby eclipsing binaries, others
are suggested to be intrinsic to the supergiant stars. In this work, we carry
out a detailed analysis of the TESS pixel data to fit the source locations of
the dominant signals reported for 17 FYPS stars with the Python package
TESS_localize. We are able to reproduce the detections of these signals for 14
of these sources, obtaining consistent source locations for four. Three of
these originate from contaminants, while the signal reported for BZ Tuc is
likely a spurious frequency introduced to the light curve of this 127-day
Cepheid by the data processing pipeline. Other signals are not significant
enough to be localized with our methods, or have long periods that are
difficult to analyze given other TESS systematics. Since no localizable signals
hold up as intrinsic pulsation frequencies of the supergiant targets, we argue
that unambiguous detection of pulsational variability should be obtained before
FYPS are considered a new class of pulsator.
