The human interface of your software package is defective.  The vendor
should have taken great pains to reduce the probability of such errors
to an insignificant level.  Your software was probably purchased from
skillful sales personnel.  It may or may not be possible to demand
improvements from the vendors.

If that "Sig i" should be "Sig 1", your software was designed by such
inept technical personnel that they don't understand the necessity of
even rudimentary error checking on input, not to mention the standards
one would expect in a program where errors could cause significant harm
to people.

Ditto.  The interface of such a package should be designed by people
who understand that doctors are often rushed and/or distracted when
they use it, and that they are unlikely to become experts at it since
they'll use it only a few minutes per day, and should compensate
for this.

The only thing you can do is try to raise the awareness of physicians
of the error-prone character of this bad and dangerous software.
Tell them to check how their input is interpreted -- surely the program
has some kind of "show me what you thought I entered" feedback
feature.

I would expect that your very reasonable and responsible and concerned
objections to the performance of this system, the selection of which is
no doubt something some manager has staked his career on, can get you
into political trouble.  Consult people who understand the power
structure in your IT department and how it relates to other parts of
the administration and the doctors.  Try as best you can not to be
typed as "anti-technology".  You aren't anti-technology, you're
anti-bad-technology.  Collect data on the types of errors, both obvious
and subtle, and statistics on their occurrence.  Then you (and the
people supporting you) will be better able to explain to the IT people
why the system is not performing adequately and how serious the problem
is.  If these errors have had effects on patient care, document this
and be prepared to explain it in laymen's terms.  Point out that such
error could result in injuries, death or even worse, lawsuits. If this
allegedly productivity enhancing system is causing you more work, do
your best to document that as well.

If at all possible get the IT people on your side against the vendor.

Good luck.  I've always had problems with politics in large
organizations which is why I recommend you consult the more politically
astute in your own organization.  If you can get a number of doctors as
concerned as you are, they will probably have a good bit more clout
then you, although they aren't necessarily the most politically aware.

I suppose the next step, if you can't get your IT department to act is
to consult your professional organization and/or upper management in your
hospital.  Note that in most entrenched bureaucracies whistle-blowers
are at substantial risk, but without them, a great deal of harm can
occur.

I have no experience with this particular application, but I've been
involved in writing, modifying, selecting, installing and training
people on applications software for nearly 30 years.  Note that many
books and technical papers have been written on the problems of
constructing an appropriate and effective user interface over the past
decades, but all too many software companies hire programmers who think
they can just figure it all out on the fly, the user can do what the
programmer is too lazy or incompetent to program in, and if the real
world is a messy place with lots of exception conditions it's not their
problem.  Unfortunately, software sells on the skills of the marketing
department, not on the skills of the designers and programmers.

Wow.  What a rant!  I could tell you 30 years of stories... It's a
disgrace that crap like your system is still making big bucks for
people who often don't know how bad the stuff is that they're writing
and selling to people who can be conned into buying it, and convinced
that if it doesn't work for them, it's all their fault.

Okay.  End of Rant.  Good luck!