Please add to the list, or comment.

These are things I notice:

being short-tempered
saying critical things, or picking something apart. (i.e. you did this wrong! It should be done another way)
not being sympathetic/empathetic (having a "deal with it" attitude)
becoming bossy about how things should be done/giving advice, and getting mad if their advice isn't taken

spending hours playing video games, or "researching" things that don't really need to be looked into, or aren't priorities. Like reading about other types of stereo speakers, after already buying some.

Or zoning out in front of the tv for long periods of time.

talking about being very "busy" but not really doing anything

Not noticing the usual Si things, like not being aware they are hungry, or just taking tylenol if they have a bad cold instead of resting/not taking care of their health/eating junk food.

staying in all of the time, and not wanting to go out

wearing the same thing every day, even when it's old

becoming freaked out if something is thrown away, such as an old towel that is ratty and stained. But they're like "that towel was originally expensive when I bought it (x number of years ago)

Becoming obsessed w/ small amounts of money, and trying to save twelve cents on cheese.

not working out

no longer working towards goals, or working apathetically towards them.

focusing only on their own needs/wants, ignoring other people's. Then getting angry and telling others they are "selfish" if they express any.

having a "poor me" attitude, but in a silent sulking way.

stonewalling.

being drawn to something totally different as an "escape." Such as picking up and moving to the Alps. Or anything not very practical.

So they basically become their opposite, with low Si and Te. And become less practical.

And I wonder if IEEs become their opposite under stress, in that we don't see new possibilities and don't encourage relationships to grow?