A problem which is being discussed in the community is not the absolute pressure, per se, but the freezing pressure resulting from melting a borehole down and having it freeze behind the penetrator.

This is also highly important for Mars where similar cryoprobes are planned. I became peripherally involved in this a year or so ago with some of the PI's of the martian Cryoscout proposal. My background in odd ices helped me to suggest some ways to tackle the problem:-

As a penetrator descends and melts its way down, it relieves the stress in the ice by melting to a lower volume. Then, it freezes again behind the penetrator. In theory, the end stress is the same as the starting stress. (ON AVERAGE, and departures from average can be important)

Depending on the rate of descent and re-freezing, & other properties such as hole size, contaminants (especially gasses such as nitrogen, oxygen, CO2), stress can be either gained or lost in the melted volume and the probe may suffer high freezing pressures due to uneven stress distribution.

There is a lot of work to be done on this, and the effect is worse for colder ambient temperatures, deeper holes, and higher gas content.

This is being looked at by some smart minds but no final answers, yet...