I was just looking at the Cubs team fielding statistics, as one does at 10pm on a Sunday night, and yikes
Outs Above Average: -9 (26th in MLB)
Fielding Run Value (runs above average): -7 (25th in MLB)
Defensive WAR: -6.5 (24th in MLB)
Defensive Runs Saved: -10 (25th in MLB)
In terms of individual players, just 4 current Cubs have at least 1 OAA this year, Swanson (2 OAA), Tauchman, Canario and PCA (all 1 OAA). For reference there are 166 players with at least 1 OAA with the league leader being Semien with 9. On the negative side, 10 players have at least -1 OAA with Morel (-4) and Madrigal, Happ and Bellinger (-2) "leading" the way.
For Fielding Run Value, there are 3 current Cubs that have at least 1, and they all have exactly 1 (Tauchman, Swanson, PCA). There are 176 players with at least 1, with the leader again being Semien with 6. There are 9 players with at least -1 FRV with Morel (-3) and Bellinger (-2) leading the way. Interestingly, Nico has -1 OAA and -1 FRV this year.
But when it comes to range, they seem to be doing pretty good:
UZR/150: 2.4 (9th in MLB)
Range RAA: 2.6 (5th in MLB)
Maybe ~30 games isn't enough time to draw anything conclusive, especially with several established solid defensive players having down starts according to this, but definitely something to maybe be at least a little concerned about.