Problema de renderização de fontes estranhas no Linux Mint 18.1 (Canela)

Question

Eu instalei o LM18.1 no laptop antigo do meu pai (Samsung P400, mais informações anexadas no final).

Há um problema de renderização estranho apenas em janelas específicas do Cinnamon:

É notável que enquanto, e. a aba do Google Chrome na parte inferior da imagem (como sebasth apontou) tem o mesmo problema, a própria aplicação não tem. Qual poderia ser a causa?

System:    Host: name-R20-P400 Kernel: 4.4.0-53-generic x86_64 (64 bit gcc: 5.4.0)
           Desktop: Cinnamon 3.2.7 (Gtk 3.18.9-1ubuntu3.3) dm: mdm Distro: Linux Mint 18.1 Serena
Machine:   System: SAMSUNG product: R20/P400 v: 07SP Chassis: type: 1
           Mobo: SAMSUNG model: R20/P400 Bios: Phoenix v: 07SP date: 01/04/2008
CPU:       Dual core Intel Core2 Duo T5450 (-MCP-) cache: 2048 KB
           flags: (lm nx sse sse2 sse3 ssse3) bmips: 6667
           clock speeds: min/max: 1000/1667 MHz 1: 1333 MHz 2: 1333 MHz
Graphics:  Card: Advanced Micro Devices [AMD/ATI] RS600M [Radeon Xpress 1250]
           bus-ID: 01:05.0 chip-ID: 1002:7942
           Display Server: X.Org 1.18.4 drivers: ati,radeon (unloaded: fbdev,vesa)
           Resolution: [email protected]
           GLX Renderer: Gallium 0.4 on ATI RS600 GLX Version: 2.1 Mesa 11.2.0 Direct Rendering: Yes
Audio:     Card Advanced Micro Devices [AMD/ATI] SBx00 Azalia (Intel HDA)
           driver: snd_hda_intel bus-ID: 00:14.2 chip-ID: 1002:4383
           Sound: Advanced Linux Sound Architecture v: k4.4.0-53-generic
Network:   Card-1: Qualcomm Atheros AR242x / AR542x Wireless Network Adapter (PCI-Express)
           driver: ath5k bus-ID: 05:00.0 chip-ID: 168c:001c
           IF: wlp5s0 state: up mac: <filter>
           Card-2: Realtek RTL-8100/8101L/8139 PCI Fast Ethernet Adapter
           driver: 8139too v: 0.9.28 port: a000 bus-ID: 0b:05.0 chip-ID: 10ec:8139
           IF: enp11s5 state: down mac: <filter>
Drives:    HDD Total Size: 202.1GB (83.5% used)
           ID-1: /dev/sda model: FUJITSU_MHY2200B size: 200.0GB serial: K42WT7C2805M
           ID-2: USB /dev/sdb model: Flash_Reader size: 2.0GB serial: 058F0O1111B-0:0
Partition: ID-1: / size: 182G used: 156G (91%) fs: ext4 dev: /dev/sda1
           ID-2: swap-1 size: 2.01GB used: 0.03GB (1%) fs: swap dev: /dev/sda5