Stock heat shields don't work

[mrantmet]

Hello,

Pre-conditions:

1. clean KSP 1.0.5.1028 taken
2. mods installed through CKAN: 64k v1.1.2 and 64k - 12 Hour Day v1.1.2
3. snadbox game created

Steps:

1. Ship: mk3 pod with stock chute, 3 small batteries and 2.5m stock heatshield + decoupler, tank, engine (all stock)
2. Ship placed on 100k circular orbit by changin save file (same story when launched normally)
3. Periapsis lowered to 30k, capsule decoupled

Result:
heat shield run out of ablator and ship explodes near 50k altitude at speed 5485m/s. Ablation rate at this point is ~7.3 kg/s, heat shield temperature before it runs out of ablator close to max for this shield.

Could you please suggest some tweaking or fix this if mod if it's supported for this KSP version and I'm not doing something wrong as per above explained.

Thanks in advance!