Error occurred x 4 this week, always when completing a 3 medal. Three times on PC using Firefox, once on iPhone using Puffin.

Very annoying!

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Now, for some advice please. Am currently levelling Alpina (slice), Sandersonia (Hit), Laurentia (Pierce), and Lavender (Magic)

Who is best after these gals out of:

SLICE:
Pentas (double damage to 2 enemies, +1-10% attack for squad based on affection)
Nasturtium (2.3 damage and drain, +10% attack for squad members)
Lupine (1.7 damage all, increased crits for squad)
Waterlily with L2 skill and two equip slots (2.4 damage, medium dodge)
Cherry Sage (2.5 damage, -10% attack for 3 enemies)

HIT:
Bipinna Cosmos (1.5 damage all, +15% Shine Crystal drop rate for squad)
Calla (event girl, 2.4 damage, +15% attack for 2 squad members)
Edelweiss (event girl, 2x damage to 2 enemies), +10% heal squad from Pest Nest Nodes)
Canna (event girl, 2.3 damage, increased critical for 2 squad members)
Adonis (event girl, 2.4 damage, +10% attack for 3 squad members)

PIERCE
Night Phlox with L2 skill and two equip slots (2.3 damage and drain HP, +15% attack for 3 squad members)
Iris (1.4 damage all, extra cannon shot)
Anthurium (2.4 damage, +22% attack for squad on turn 1)
Madonna (1.4 damage to enemies 3 times, +10-30% Attack Power each Solar Blast used)

MAGIC:
Epidendrum (2.3x damage, +1.5 activation self for first turn)
Strawberry Candle with two equip slots (2.5x damage, 2-3 normal nodes turned into solar nodes)
Queen of the Night with two equip slots (x3 damage to 2 enemies, 2x squad healing)
Evening Primrose (x2 damage to 2 enemies, +10% Attack power for squad)
German Iris (2.5x damage, +25% Solar Blast damage)

Thanks for any tips!