Hs-Tp distribution plot strange return value contours

[efvik]

I'm seeing some strange behaviour of plots.plot_joint_distribution_Hs_Tp().

fig = plots.plot_joint_distribution_Hs_Tp(values,'Significant_Wave_Height_Hm0','Wave_Peak_Period')

With density:

This is my data:

Significant_Wave_Height_Hm0 | Wave_Peak_Period

4.543965 | 14.377853
4.552460 | 14.389552
4.536097 | 14.417733
4.551234 | 14.397633
4.493371 | 14.302602
... | ...
1.157736 | 10.076883
1.109909 | 10.098418
1.075126 | 10.104949
1.028762 | 10.130224
0.995882 | 10.130013

Significant_Wave_Height_Hm0 Wave_Peak_Period
count 433536.000000 433536.000000
mean 1.909155 9.739225
std 1.184960 1.983180
min 0.010000 3.175204
25% 1.040708 8.300000
50% 1.632867 9.581067
75% 2.478007 11.000000
max 12.492237 21.500000